Mitochondrial dysfunction and sarcopenia of aging: from signaling pathways to clinical trials

Adipose tissue in older individuals: a contributing factor to sarcopenia

Sarcopenia is a geriatric syndrome characterized by a functional decline in muscle. The prevalence of sarcopenia increases with natural aging, becoming a serious health problem among elderly individuals. Therefore, understanding the pathology of sarcopenia is critical for inhibiting age-related alterations and promoting health and longevity in elderly individuals. The development of sarcopenia may be influenced by interactions between visceral and subcutaneous adipose tissue and skeletal muscle, particularly under conditions of chronic low-grade inflammation and metabolic dysfunction. This hypothesis is supported by the following observations: (i) accumulation of senescent cells in both adipose tissue and skeletal muscle with age; (ii) gut dysbiosis, characterized by an imbalance in gut microbial communities as the main trigger for inflammation, sarcopenia, and aged adipose tissue; and (iii) microbial dysbiosis, which could impact the onset or progression of a senescent state. Moreover, adipose tissue acts as an endocrine organ, releasing molecules that participate in intricate communication networks between organs. Our discussion focuses on novel adipokines and their role in regulating adipose tissue and muscle, particularly those influenced by aging and obesity, emphasizing their contributions to disease development. On the basis of these findings, we propose that age-related adipose tissue and sarcopenia are disorders characterized by chronic inflammation and metabolic dysregulation. Finally, we explore new potential therapeutic strategies involving specialized proresolving mediator (SPM) G protein-coupled receptor (GPCR) agonists, non-SPM GPCR agonists, transient receptor potential (TRP) channels, antidiabetic drugs in conjunction with probiotics and prebiotics, and compounds designed to target senescent cells and mitigate their pro-inflammatory activity.

Sarcopenia in cirrhosis: From pathophysiology to interventional therapy

Sarcopenia, characterized by the loss of skeletal muscle mass and function, is a significant complication in patients with cirrhosis. This condition not only exacerbates the overall morbidity and mortality associated with liver disease but also complicates patient management, increasing the risk of hospitalization, infections, and hepatic encephalopathy. Despite its clinical significance, sarcopenia in cirrhotic patients remains underdiagnosed and undertreated. This review aims to summarize current knowledge on the pathophysiology of sarcopenia in cirrhosis, including mechanisms such as altered metabolism, hormonal imbalances, and inflammation. Additionally, we explore diagnostic challenges and discuss emerging therapeutic strategies, including nutritional support, exercise, and pharmacological interventions. By highlighting the gaps in existing research and proposing directions for future studies, this review seeks to improve the management and outcomes of cirrhotic patients affected by sarcopenia.

Artificial neural network inference analysis identified novel genes and gene interactions associated with skeletal muscle aging

BACKGROUND

Sarcopenia is an age-related muscle disease that increases the risk of falls, disabilities, and death. It is associated with increased muscle protein degradation driven by molecular signalling pathways including Akt and FOXO1. This study aims to identify genes, gene interactions, and molecular pathways and processes associated with muscle aging and exercise in older adults that remained undiscovered until now leveraging on an artificial intelligence approach called artificial neural network inference (ANNi).

METHODS

Four datasets reporting the profile of muscle transcriptome obtained by RNA-seq of young (21-43 years) and older adults (63-79 years) were selected and retrieved from the Gene Expression Omnibus (GEO) data repository. Two datasets contained the transcriptome profiles associated to muscle aging and two the transcriptome linked to resistant exercise in older adults, the latter before and after 6 months of exercise training. Each dataset was individually analysed by ANNi based on a swarm neural network approach integrated into a deep learning model (Intelligent Omics). This allowed us to identify top 200 genes influencing (drivers) or being influenced (targets) by aging or exercise and the strongest interactions between such genes. Downstream gene ontology (GO) analysis of these 200 genes was performed using Metacore (Clarivate™) and the open-source software, Metascape. To confirm the differential expression of the genes showing the strongest interactions, real-time quantitative PCR (RT-qPCR) was employed on human muscle biopsies obtained from eight young (25 ± 4 years) and eight older men (78 ± 7.6 years), partaking in a 6-month resistance exercise training programme.

RESULTS

CHAD, ZDBF2, USP54, and JAK2 were identified as the genes with the strongest interactions predicting aging, while SCFD1, KDM5D, EIF4A2, and NIPAL3 were the main interacting genes associated with long-term exercise in older adults. RT-qPCR confirmed significant upregulation of USP54 (P = 0.005), CHAD (P = 0.03), and ZDBF2 (P = 0.008) in the aging muscle, while exercise-related genes were not differentially expressed (EIF4A2 P = 0.99, NIPAL3 P = 0.94, SCFD1 P = 0.94, and KDM5D P = 0.64). GO analysis related to skeletal muscle aging suggests enrichment of pathways linked to bone development (adj P-value 0.006), immune response (adj P-value <0.001), and apoptosis (adj P-value 0.01). In older exercising adults, these were ECM remodelling (adj P-value <0.001), protein folding (adj P-value <0.001), and proteolysis (adj P-value <0.001).

CONCLUSIONS

Using ANNi and RT-qPCR, we identified three strongly interacting genes predicting muscle aging, ZDBF2, USP54, and CHAD. These findings can help to inform the design of nonpharmacological and pharmacological interventions that prevent or mitigate sarcopenia.

Betaine delays age-related muscle loss by mitigating Mss51-induced impairment in mitochondrial respiration via Yin Yang1

BACKGROUND

Mitochondrial dysfunction is one of the hallmarks of aging and a leading contributor to sarcopenia. Nutrients are essential for improving mitochondrial function and skeletal muscle health during the aging process. Betaine is a nutrient with potential muscle-preserving properties. However, whether and how betaine could regulate the mitochondria function in aging muscle are poorly understood. We aimed to explore the molecular target and underlying mechanism of betaine in attenuating the age-related mitochondrial dysfunction in skeletal muscle.

METHODS

Young mice (YOU, 2 months), old mice (OLD, 15 months), and old mice with betaine treatment (BET, 15 months) were fed for 12 weeks. The effects of betaine on muscle mass, strength, function, and subcellular structure of muscle fibres were assessed. RNA sequencing (RNA-seq) was conducted to identify the molecular target of betaine. The impacts of betaine on mitochondrial-related molecules, superoxide accumulation, and oxidative respiration were examined using western blotting (WB), immunofluorescence (IF) and seahorse assay. The underlying mechanism of betaine regulation on the molecular target to maintain mitochondrial function was investigated by luciferase reporter assay, chromatin immunoprecipitation and electrophoretic mobility shift assay. Adenoassociated virus transfection, succinate dehydrogenase staining (SDH), and energy expenditure assessment were performed on 20-month-old mice for validating the mechanism in vivo.

RESULTS

Betaine intervention demonstrated anti-aging effects on the muscle mass (P = 0.017), strength (P = 0.010), and running distance (P = 0.013). Mitochondrial-related markers (ATP5a, Sdha, and Uqcrc2) were 1.1- to 1.5-fold higher in BET than OLD (all P ≤ 0.036) with less wasted mitochondrial vacuoles accumulating in sarcomere. Bioinformatic analysis from RNA-seq displayed pathways related to mitochondrial respiration activity was higher enriched in BET group (NES = -0.87, FDR = 0.10). The quantitative real time PCR (qRT-PCR) revealed betaine significantly reduced the expression of a novel mitochondrial regulator, Mss51 (-24.9%, P = 0.002). In C2C12 cells, betaine restored the Mss51-mediated suppression in mitochondrial respiration proteins (all P ≤ 0.041), attenuated oxygen consumption impairment, and superoxide accumulation (by 20.7%, P = 0.001). Mechanically, betaine attenuated aging-induced repression in Yy1 mRNA expression (BET vs. OLD: 2.06 vs. 1.02, P = 0.009). Yy1 transcriptionally suppressed Mss51 mRNA expression both in vitro and in vivo. This contributed to the preservation of mitochondrial respiration, improvement for energy expenditure (P = 0.008), and delay of muscle loss during aging process.

CONCLUSIONS

Altogether, betaine transcriptionally represses Mss51 via Yy1, improving age-related mitochondrial respiration in skeletal muscle. These findings suggest betaine holds promise as a dietary supplement to delay skeletal muscle degeneration and improve age-related mitochondrial diseases.

Mendelian randomization analysis reveals no causal relationship between thyroid function and sarcopenia-related traits

Background

Recent research has indicated a potential association between thyroid function and sarcopenia, but the specific mechanisms and a definitive causal relationship have yet to be established. Therefore, the objective of this study is to examine the potential causal connection between thyroid function and sarcopenia-related traits, including hand-grip strength, appendicular lean mass (ALM), and walking pace.

Methods

The study used a bi-directional two-sample MR design, with thyroid function examined as the exposure and sarcopenia-related traits as the outcome in the first stage, and then reversed in the second stage. The genetic instruments for thyroid function were obtained from a comprehensive meta-analysis involving 271,040 participants. Data on sarcopenia-related traits based on GWASs were collected from the UK Biobank, which includes up to 461,026 European participants. The estimates for MR were calculated using the inverse-variance weighted (IVW) method, and several sensitivity analyses were performed.

Results

After applying the Bonferroni correction for multiple testing, our MR analyses revealed no significant impact of thyroid function liability on sarcopenia-related traits. Similarly, our reverse MR analysis did not provide evidence supporting the influence of liability to sarcopenia-related traits on thyroid function. The results of the primary IVW MR analyses were largely in line with those obtained from our sensitivity MR analyses.

Conclusion

Our research findings do not suggest a link between thyroid function and sarcopenia-related traits. The associations identified in epidemiological studies may be influenced, at least in part, by shared biological mechanisms or environmental confounders.

Preparation of Rutin-Whey Protein Pickering Emulsion and Its Effect on Zebrafish Skeletal Muscle Movement Ability

Nutritional supplementation enriched with protein and antioxidants has been demonstrated to effectively strengthen skeletal muscle function and mitigate the risk of sarcopenia. Dietary protein has also been a common carrier to establish bioactive delivery system. Therefore, in this study, a Pickering emulsion delivery system for rutin was constructed with whey protein, and its structural characteristics, bioaccessibility, and molecular interactions were investigated. In the in vivo study, zebrafish (n = 10 in each group), which have a high genetic homology to humans, were treated with dexamethasone to induce sarcopenia symptoms and were administered with rutin, whey protein and the Pickering emulsion, respectively, for muscle movement ability evaluation, and zebrafish treated with or without dexamethasone was used as the model and the control groups, respectively. Results showed that the Pickering emulsion was homogeneous in particle size with a rutin encapsulation rate of 71.16 ± 0.15% and loading efficiency of 44.48 ± 0.11%. Rutin in the Pickering emulsion exhibited a significantly higher bioaccessibility than the free form. The interaction forces between rutin and the two components of whey proteins (α-LA and β-LG) were mainly van der Waals forces and hydrogen bonds. After treatment for 96 h, the zebrafish in Picking emulsion groups showed a significantly increased high-speed movement time and frequency, an increased level of ATP, prolonged peripheral motor nerve length, and normalized muscular histological structure compared with those of the model group (p < 0.05). The results of this study developed a new strategy for rutin utilization and provide scientific evidence for sarcopenia prevention with a food-derived resource.

A causal relationship between sarcopenia and cognitive impairment: A Mendelian randomization study

OBJECTIVE

Sarcopenia and cognitive impairment often coexist in the elderly. In this study, we investigated the causal relationship between sarcopenia-related muscle characteristics and cognitive performance.

METHODS

We used linkage disequilibrium score regression (LDSC) and Mendelian Randomization (MR) analyses to estimate genetic correlations and causal relationships between genetically predicted sarcopenia-related muscle traits and cognitive function, as well as cognitive function-based discovery samples and replicated samples. Estimated effect sizes were derived from a fixed-effects meta-analysis.

RESULTS

Our univariate genome-wide association study (GWAS) meta-analysis indicated a causal relationship between appendicular lean mass (ALM) (β = 0.049; 95% confidence interval (CI): 0.032-0.066, P < 0.001) and walking pace (β = 0.349; 95% CI: 0.210-0.487, P < 0.001) with cognitive function, where a causal relationship existed between ALM in both male and female (βALM-Male(M) = 0.060; 95% CI: 0.031-0.089, PALM-M < 0.001; βALM-Female(F) = 0.045; 95% CI: 0.020-0.069, PALM-F < 0.001) with cognitive function. Low grip strength was not causally associated with cognitive function (β = -0.045; 95% CI: -0.092 - -0.002, P = 0.062). A reverse causality GWAS meta-analysis showed a causal relationship between cognitive function and ALM (β = 0.033; 95% CI: 0.018-0.048, P < 0.001) and walking pace (β = 0.039; 95% CI: 0.033-0.051, P < 0.001), where ALM in both male and female showed a causality (βALM-M = 0.041; 95% CI: 0.019-0.063, PALM-M < 0.001; βALM-F = 0.034; 95% CI: 0.010-0.058, PALM-F = 0.005). Cognitive function was not causally related to low grip strength (β = -0.024; 95% CI: -0.073-0.025, P = 0.344). Multivariable MR1 (MVMR1) analyses showed a significant causal relationship for ALM (β = 0.077; 95% CI: 0.044-0.109, P = 0.000) and walking pace (β = 0.579; 95% CI: 0.383-0.775, P = 0.000) and cognitive function. Multivariable MR2 (MVMR2) multivariate analysis showed that ALM causality remained (β = 0.069; 95% CI: 0.033-0.106, P = 0.000), and walking pace (β = 0.589; 95% CI: 0.372-0.806, P = 0.000).

CONCLUSIONS

Bidirectional two-sample MR demonstrated that sarcopenia-related muscle characteristics and cognitive performance were positive causal genetic risk factors for each other, while a multivariable MR study demonstrated that low ALM and a slow walking pace were causally involved in reduced cognitive performance. This study suggests a causal relationship between sarcopenia and cognitive impairment in older adults and provide new ideas for prevention and treatment.

Action of melatonin and physical exercise on the liver of cirrhotic rats: Study of oxidative stress and the inflammatory process

Background and Aim

Cirrhosis is characterized by structural and functional alterations of the liver. Melatonin (MLT) has antioxidant properties. Physical exercise (EX) can reverse muscle loss in cirrhotic patients. The objective was to evaluate the action of MLT and EX on the liver of rats subjected to the experimental model of bile duct ligation (BLD).

Materials and Methods

48 male Wistar rats were used, divided into groups: Control (CO), CO+MLT, CO+EX, CO+MLT+EX, BDL, BDL+MLT, BDL+EX, and BDL+MLT+EX. The treatments occurred from the 15th to the 28th day. The dose of MLT was 20 mg/kg via I.p (1x/day), and the EX was performed 10 min/day. Blood and liver were collected for analysis.

Results

The liver integrity enzymes AST, ALT, and ALP showed a significant reduction in the groups treated with MLT and EX. Histological analyses showed reorganization of the liver parenchyma, reduction of inflammatory infiltrate, and fibrotic nodules. Lipoperoxidation (LPO), the activity of antioxidant enzymes, and nitric oxide metabolites showed a significant reduction in the groups treated with MLT and EX. The expression of TNF-α and NF-kB decreased in the treated groups.

Conclusion

Melatonin and physical exercise seem to be effective in restoring the parameters evaluated in this model of experimental cirrhosis.

Comparative effects of lifelong moderate-intensity continuous training and high-intensity interval training on blood lipid levels and mental well-being in naturally ageing mice

OBJECTIVE

This study aimed to investigate the impact of lifelong exercise, including both moderate-intensity continuous training and high-intensity interval training, on blood lipid levels and mental behaviour in naturally ageing mice to identify effective exercise strategies for ageing-related health issues.

METHODS

Six-week-old male BALB/c mice were randomly assigned to one of four groups: young control (YC), natural ageing control (OC), lifelong moderate-intensity continuous exercise (EM), and lifelong high-intensity interval exercise (EH) groups. The EM group was trained at a speed corresponding to 70 % of the maximum running speed, while the EH group was trained at a running speed alternating between 50 % of the maximum running speed, 70 % of the maximum running speed, and 90 % of the maximum running speed. All exercise sessions were conducted three times per week, with each session lasting 50 min. Behavioural tests and blood sample collection were conducted at 72 weeks of age.

RESULTS

Ageing in mice led to changes in muscle and fat mass. Both the EM and EH groups showed greater muscle mass and lower fat mass than did the OC group. Ageing was associated with elevated anxiety (fewer open arm entries, time spent in the central region) and depression (lower sucrose preference) indicators. However, these changes were reversed in both exercise groups, with no differences between the two exercise groups. Blood lipid levels, including total cholesterol (TC), total triglycerides (TGs), low-density lipoprotein (LDL), and free fatty acid (FFA) levels, were greater in the OC group than in the YC group. Additionally, the OC group exhibited lower high-density lipoprotein (HDL) levels. However, both the EM and EH groups exhibited improved lipid profiles compared to those of the YC group.

CONCLUSION

Lifelong exercise, whether moderate-intensity continuous or high-intensity interval training, can preserve body health during ageing, prevent anxiety and depression, and maintain stable blood lipid levels. Both exercise types are equally effective, suggesting that exercise intensity may not be the critical factor underlying these beneficial adaptations.

Influence of human gut microbiome on the healthy and the neurodegenerative aging

The gut microbiome plays a crucial role in host health throughout the lifespan by influencing brain function during aging. The microbial diversity of the human gut microbiome decreases during the aging process and, as a consequence, several mechanisms increase, such as oxidative stress, mitochondrial dysfunction, inflammatory response, and microbial gut dysbiosis. Moreover, evidence indicates that aging and neurodegeneration are closely related; consequently, the gut microbiome may serve as a novel marker of lifespan in the elderly. In this narrative study, we investigated how the changes in the composition of the gut microbiome that occur in aging influence to various neuropathological disorders, such as mild cognitive impairment (MCI), dementia, Alzheimer's disease (AD), and Parkinson's disease (PD); and which are the possible mechanisms that govern the relationship between the gut microbiome and cognitive impairment. In addition, several studies suggest that the gut microbiome may be a potential novel target to improve hallmarks of brain aging and to promote healthy cognition; therefore, current and future therapeutic interventions have been also reviewed.

Mitochondria as Nutritional Targets to Maintain Muscle Health and Physical Function During Ageing

The age-related loss of skeletal muscle mass and physical function leads to a loss of independence and an increased reliance on health-care. Mitochondria are crucial in the aetiology of sarcopenia and have been identified as key targets for interventions that can attenuate declines in physical capacity. Exercise training is a primary intervention that reduces many of the deleterious effects of ageing in skeletal muscle quality and function. However, habitual levels of physical activity decline with age, making it necessary to implement adjunct treatments to maintain skeletal muscle mitochondrial health and physical function. This review provides an overview of the effects of ageing and exercise training on human skeletal muscle mitochondria and considers several supplements that have plausible mechanistic underpinning to improve physical function in ageing through their interactions with mitochondria. Several supplements, including MitoQ, urolithin A, omega-3 polyunsaturated fatty acids (n3-PUFAs), and a combination of glycine and N-acetylcysteine (GlyNAC) can improve physical function in older individuals through a variety of inter-dependent mechanisms including increases in mitochondrial biogenesis and energetics, decreases in mitochondrial reactive oxygen species emission and oxidative damage, and improvements in mitochondrial quality control. While there is evidence that some nicotinamide adenine dinucleotide precursors can improve physical function in older individuals, such an outcome seems unrelated to and independent of changes in skeletal muscle mitochondrial function. Future research should investigate the safety and efficacy of compounds that can improve skeletal muscle health in preclinical models through mechanisms involving mitochondria, such as mitochondrial-derived peptides and mitochondrial uncouplers, with a view to extending the human health-span.

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.

Research Progress on Patients of Esophageal Cancer Complicated with Sarcopenia

Aims/Background The application of immunochemotherapy has significantly enhanced the quality of life and overall survival of patients with esophageal cancer. Sarcopenia, which is increasingly prevalent in these patients, markedly affects prognosis, but can be reversed by appropriate and effective treatment. Methods The narrative review was conducted on PubMed using the keywords ("esophageal" or "esophagus" and "sarcopenia"). Results This article reviews the measurement, timing, and intervention strategies for sarcopenia in patients with esophageal cancer. It summarizes the evaluation indicators of skeletal muscle loss in these patients, analyzes the barriers to intervention for frailty among esophageal cancer patients, and proposes corresponding countermeasures. Conclusion Patients with esophageal cancer often suffer from severe sarcopenia. Clinical intervention is crucial in addressing this issue.

Altered mitochondrial homeostasis on bisphenol-A exposure and its association in developing polycystic ovary syndrome: A comprehensive review

Polycystic ovary syndrome (PCOS) is a heterogeneous endocrinopathy that is known to be one of the most common reproductive pathologies observed in premenopausal women around the globe and is particularly complex as it affects various endocrine and reproductive metabolic pathways. Endocrine-disrupting chemicals (EDCs) are considered to be environmental toxicants as they have hazardous health effects on the functioning of the human endocrine system. Among various classes of EDCs, bisphenol A (BPA) has been under meticulous investigation due to its ability to alter the endocrine processes. As there is emerging evidence suggesting that BPA-induced mitochondrial homeostasis dysfunction in various pathophysiological conditions, this review aims to provide a detailed review of how various pathways associated with ovarian mitochondrial homeostasis are impaired on BPA exposure and its mirroring effects on the PCOS phenotype. BPA exposure might cause significant damage to the mitochondrial morphology and functions through the generation of reactive oxygen species (ROS) and simultaneously downregulates the total antioxidant capacity, thereby leading to oxidative stress. BPA disrupts the mitochondrial dynamics in human cells by altering the expressions of mitochondrial fission and fusion genes, increases the senescence marker proteins, along with significant alterations in the mTOR/AMPK pathway, upregulates the expression of autophagy mediating factors, and downregulates the autophagic suppressor. Furthermore, an increase in apoptosis of the ovarian granulosa cells indicates impaired folliculogenesis. As all these key features are associated with the pathogenesis of PCOS, this review can provide a better insight into the possible associations between BPA-induced dysregulation of mitochondrial homeostasis and PCOS.

Association between coffee intake and skeletal muscle mass among U.S. adults: a population-based study

Background

A limited number of studies have reported that the possible effects of coffee intake on skeletal muscle mass, but the results have been inconsistently conclusive and there are no large sample studies concerning the U.S. population. Therefore, the purpose of our study was to explore the connection between coffee consumption and skeletal muscle mass in U.S. adults.

Methods

The population for this cross-sectional study was drawn from the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2018. Appendicular lean mass was accurately obtained from DXA, and skeletal muscle mass was assessed using appendicular skeletal muscle mass adjusted for body mass index (ASMBMI). Coffee and caffeine consumptions were obtained on a 24-h dietary recall questionnaire. Furthermore, the associations between coffee and caffeine intake and skeletal muscle mass were evaluated using three multiple linear regression models and smoothed curve fitting. Subgroup analyses based on age, gender, ethnicity and body mass index (BMI) were performed to assess the robustness of these relationships.

Results

This cross-sectional survey included a total of 8,333 participants. After adjusting for all covariates, higher intake of coffee, caffeinated coffee, and caffeine was associated with elevated ASMBMI (coffee: β = 0.01, 95% CI: 0.01, 0.02, P-value < 0.001; caffeinated coffee: β = 0.01, 95% CI: 0.01, 0.02, P-value < 0.001; caffeine: β = 0.02, 95% CI: 0.01, 0.04, P-value < 0.001). Meanwhile, smoothed curve fitting showed that coffee, caffeinated coffee, and caffeine intake were linearly and positively associated with ASMBMI. After further stratification by sex, age, and ethnicity, the positive relationships between coffee (especially caffeinated coffee) and caffeine intake and ASMBMI were not modified (P for interaction > 0.05). However, these relationships disappeared when the BMI over 30 kg/m2.

Conclusions

In general, consumption of coffee and caffeine is positively associated with skeletal muscle mass. Therefore, an appropriate increase in coffee and caffeine intake may be advocated in populations at high risk for low skeletal muscle mass.

The Emerging Role of the Mitochondrial Respiratory Chain in Skeletal Aging

Maintenance of mitochondrial homeostasis is crucial for ensuring healthy mitochondria and normal cellular function. This process is primarily responsible for regulating processes that include mitochondrial OXPHOS, which generates ATP, as well as mitochondrial oxidative stress, apoptosis, calcium homeostasis, and mitophagy. Bone mesenchymal stem cells express factors that aid in bone formation and vascular growth. Positive regulation of hematopoietic stem cells in the bone marrow affects the differentiation of osteoclasts. Furthermore, the metabolic regulation of cells that play fundamental roles in various regions of the bone, as well as interactions within the bone microenvironment, actively participates in regulating bone integrity and aging. The maintenance of cellular homeostasis is dependent on the regulation of intracellular organelles, thus understanding the impact of mitochondrial functional changes on overall bone metabolism is crucially important. Recent studies have revealed that mitochondrial homeostasis can lead to morphological and functional abnormalities in senescent cells, particularly in the context of bone diseases. Mitochondrial dysfunction in skeletal diseases results in abnormal metabolism of bone-associated cells and a secondary dysregulated microenvironment within bone tissue. This imbalance in the oxidative system and immune disruption in the bone microenvironment ultimately leads to bone dysplasia. In this review, we examine the latest developments in mitochondrial respiratory chain regulation and its impacts on maintenance of bone health. Specifically, we explored whether enhancing mitochondrial function can reduce the occurrence of bone cell deterioration and improve bone metabolism. These findings offer prospects for developing bone remodeling biology strategies to treat age-related degenerative diseases.

SIRT1 signaling pathways in sarcopenia: Novel mechanisms and potential therapeutic targets

Sarcopenia is an aging-related skeletal disease characterized by decreased muscle mass, strength, and physical function, severely affecting the quality of life (QoL) of the elderly population. Sirtuin 1 (SIRT1), as a nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylases, has been reported to participate in various aging-related signaling pathways and exert protective effect on many human diseases. SIRT1 functioned as an important role in the occurrence and progression of sarcopenia through regulating key pathways related to protein homeostasis, apoptosis, mitochondrial dysfunction, insulin resistance and autophagy in skeletal muscle, including SIRT1/Forkhead Box O (FoxO), AMP-activated protein kinase (AMPK)/SIRT1/nuclear factor κB (NF-κB), SIRT1/p53, AMPK/SIRT1/peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), and SIRT1/live kinase B1 (LKB1)/AMPK pathways. However, the specific mechanisms of these processes have not been fully illuminated. Currently, several SIRT1-mediated interventions on sarcopenia have been preliminarily developed, such as SIRT1 activator polyphenolic compounds, exercising and calorie restriction. In this review, we summarized the predominant mechanisms of SIRT1 involved in sarcopenia and therapeutic modalities targeting the SIRT1 signaling pathways for the prevention and prognosis of sarcopenia.

Aging-dependent mitochondrial bioenergetic impairment in the skeletal muscle of NNT-deficient mice

Overall health relies on features of skeletal muscle that generally decline with age, partly due to mechanisms associated with mitochondrial redox imbalance and bioenergetic dysfunction. Previously, aged mice genetically devoid of the mitochondrial NAD(P)+ transhydrogenase (NNT, encoded by the nicotinamide nucleotide transhydrogenase gene), an enzyme involved in mitochondrial NADPH supply, were shown to exhibit deficits in locomotor behavior. Here, by using young, middle-aged, and older NNT-deficient (Nnt-/-) mice and age-matched controls (Nnt+/+), we aimed to investigate how muscle bioenergetic function and motor performance are affected by NNT expression and aging. Mice were subjected to the wire-hang test to assess locomotor performance, while mitochondrial bioenergetics was evaluated in fiber bundles from the soleus, vastus lateralis and plantaris muscles. An age-related decrease in the average wire-hang score was observed in middle-aged and older Nnt-/- mice compared to age-matched controls. Although respiratory rates in the soleus, vastus lateralis and plantaris muscles did not significantly differ between the genotypes in young mice, the rates of oxygen consumption did decrease in the soleus and vastus lateralis muscles of middle-aged and older Nnt-/- mice. Notably, the soleus, which exhibited the highest NNT expression level, was the muscle most affected by aging, and NNT loss. Additionally, histology of the soleus fibers revealed increased numbers of centralized nuclei in older Nnt-/- mice, indicating abnormal morphology. In summary, our findings suggest that NNT expression deficiency causes locomotor impairments and muscle dysfunction during aging in mice.

Musculoskeletal Dimension and Brightness Reference Values in Lumbar Magnetic Resonance Imaging-A Radio-Anatomic Investigation in 80 Healthy Adult Individuals

Background/Objectives: Magnetic resonance imaging (MRI) is the preferred diagnostic means to visualize spinal pathologies, and offers the possibility of precise structural tissue analysis. However, knowledge about MRI-based measurements of physiological cross-sectional musculoskeletal dimensions and associated tissue-specific average structural brightness in the lumbar spine of healthy young women and men is scarce. The current study was planned to investigate characteristic intersexual differences and to provide MRI-related musculoskeletal baseline values before the onset of biological aging. Methods: At a single medical center, lumbar MRI scans of 40 women and 40 men aged 20-40 years who presented with moderate nonspecific low back pain were retrospectively evaluated for sex-specific differences in cross-sectional sizes of the fifth lumbar vertebrae, psoas and posterior paravertebral muscles, and respective sex- and age-dependent average brightness alterations on T2-weighted axial sections in the L5-level. Results: In women (mean age 33.5 years ± 5.0 (standard deviation)), the investigated musculoskeletal cross-sectional area sizes were significantly smaller (p < 0.001) compared to those in men (mean age 33.0 years ± 5.7). Respective average musculoskeletal brightness values were higher in women compared to those in men, and most pronounced in posterior paravertebral muscles (p < 0.001). By correlating brightness results to those of subcutaneous fat tissue, all intersexual differences, including those between fifth lumbar vertebrae and psoas muscles, turned out to be statistically significant. This phenomenon was least pronounced in psoas muscles. Conclusions: Lumbar musculoskeletal parameters showed significantly larger dimensions of investigated anatomical structures in men compared to those in women aged 20-40 years, and an earlier onset and faster progress of bone loss and muscle degradation in women.

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.

TP53INP2-dependent activation of muscle autophagy ameliorates sarcopenia and promotes healthy aging

Sarcopenia is a major contributor to disability in older adults, and thus, it is key to elucidate the mechanisms underlying its development. Increasing evidence suggests that impaired macroautophagy/autophagy contributes to the development of sarcopenia. However, the mechanisms leading to reduced autophagy during aging remain largely unexplored, and whether autophagy activation protects from sarcopenia has not been fully addressed. Here we show that the autophagy regulator TP53INP2/TRP53INP2 is decreased during aging in mouse and human skeletal muscle. Importantly, chronic activation of autophagy by muscle-specific overexpression of TRP53INP2 prevents sarcopenia and the decline of muscle function in mice. Acute re-expression of TRP53INP2 in aged mice also improves muscle atrophy, enhances mitophagy, and reduces ROS production. In humans, high levels of TP53INP2 in muscle are associated with increased muscle strength and healthy aging. Our findings highlight the relevance of an active muscle autophagy in the maintenance of muscle mass and prevention of sarcopenia.Abbreviation: ATG7: autophagy related 7; BMI: body mass index; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; ROS: reactive oxygen species; TP53INP2: tumor protein p53 inducible nuclear protein 2; WT: wild type.

Predictors for the development of motoric cognitive risk syndrome in older adults

BACKGROUND

Motoric cognitive risk (MCR) syndrome refers to a condition where both slow gait and memory complaints coexist, which heightens their vulnerability to developing dementia. Considering that the risk factors of MCR are elucidated from cross-sectional studies and also likely vary based on socioeconomic status, we conducted a community-based longitudinal study to determine the predictors of MCR among older adults in Malaysia.

METHODS

Out of 1,249 older participants (aged 60 years and above) without MCR at baseline (Wave II of LRGS-TUA cohort study), 719 were successfully followed up after 3.5 years to identify predictors of subsequent MCR development. A comprehensive interview-based questionnaire was administered for sociodemographic information, cognitive function, psychosocial, functional status, and dietary intake. Anthropometric measurements, body composition, and physical performance were assessed. Univariate analyses were performed for each variable, followed by a hierarchical logistic regression analysis to identify the predictors of MCR that accounted for confounding effects between the studied factors.

RESULTS

The incidence rate of MCR was 4.0 per 100 person-years. Smoking (Adjusted Odd Ratio (Adj OR) = 1.782; 95% Confidence Interval (CI):1.050-3.024), hypertension (Adj OR = 1.725; 95% CI:1.094-2.721), decreased verbal memory as assessed by the lower Rey Auditory Verbal Learning Test (RAVLT) (Adj OR = 1.891; 95% CI:1.103-3.243), and decreased functional status measured using instrumental activity of daily living (IADL) (Adj OR = 4.710; 95% CI:1.319-16.823), were predictors for MCR incidence.

CONCLUSIONS

Our study results provide an initial reference for future studies to formulate effective preventive management and intervention strategies to reduce the growing burden of adverse health outcomes, particularly among Asian older adults.

Exercise-induced signaling activation by Chrysanthemum zawadskii and its active compound, linarin, ameliorates age-related sarcopenia through Sestrin 1 regulation

BACKGROUND

Exercise is an effective strategy to prevent sarcopenia, but high physical inactivity in the elderly requires alternative therapeutic approaches. Exercise mimetics are therapeutic compounds that simulate the beneficial effects of exercise on skeletal muscles. However, the toxicity and adverse effects of exercise mimetics raise serious concerns.

PURPOSE

We aimed to search novel plant-based alternatives to activate exercise induced-signaling.

METHODS

We used open databases and luciferase assays to identify plant-derived alternatives to activate exercise-induced signaling and compared its efficacy to mild intensity continuous training (MICT) in aged C57BL/6 mice. The nineteen-month-old mice were either fed an experimental diet supplemented with the isolated alternative or subjected to MICT for up to 21 mo of age.

RESULTS

Our analysis revealed that Chrysanthemum zawadskii Herbich var latillobum (Maxim.) Kitamura (CZH), a medicinal plant rich in linarin, is a novel activator of peroxisome proliferator-activated receptor δ (PPARδ) and estrogen-related receptor γ (ERRγ), key regulators of exercise-induced positive effects on muscles. CZH supplementation ameliorated the loss of muscle function and mass, and increased PPARδ and ERRγ expression in mouse muscles. CZH also improved mitochondrial functions and proteostasis in aged mice, similar to MICT. Furthermore, CZH and linarin induced the activation of Sestrin 1, a key mediator of exercise benefits, in muscle. Silencing Sestrin 1 negated the increase in myogenesis and mitochondrial respiration by CZH and linarin in primary myoblasts from old mice.

CONCLUSION

Our findings suggest the potential of CZH as a novel plant-derived alternative to activate exercise-induced signaling for preventing sarcopenia in sedentary older adults. This could offer a safer therapeutic option for sarcopenia treatment.

Biomarkers of frailty

Several biomarkers have been proposed to identify frailty, a multisystemic age-related syndrome. However, the complex pathophysiology and the absence of a consensus on a comprehensive and universal definition make it challenging to pinpoint a singular biomarker or set of biomarkers that conclusively characterize frailty. This review delves into the main laboratory biomarkers, placing special emphasis on those associated with various pathways closely tied to the frailty condition, such as inflammation, oxidative stress, mitochondrial dysfunction, metabolic and endocrine alterations and microRNA. Additionally, we provide a summary of different clinical biomarkers encompassing different tools that have been proposed to assess frailty. We further address various imaging biomarkers such as Dual Energy X-ray Absorptiometry, Bioelectrical Impedance analysis, Computed Tomography and Magnetic Resonance Imaging, Ultrasound and D3 Creatine dilution. Intervention to treat frailty, including non-pharmacological ones, especially those involving physical exercise and nutrition, and pharmacological interventions, that include those targeting specific mechanisms such as myostatin inhibitors, insulin sensitizer metformin and with special relevance for hormonal treatments are mentioned. We further address the levels of different biomarkers in monitoring the potential positive effects of some of these interventions. Despite the availability of numerous biomarkers, their performance and usefulness in the clinical arena are far from being satisfactory. Considering the multicausality of frailty, there is an increasing need to assess the role of sets of biomarkers and the combination between laboratory, clinical and image biomarkers, in terms of sensitivity, specificity and predictive values for the diagnosis and prognosis of the different outcomes of frailty to improve detection and monitoring of older people with frailty or at risk of developing it, being this a need in the everyday clinical practice.

The effect of low birth weight as an intrauterine exposure on the early onset of sarcopenia through possible molecular pathways

Sarcopenia, a musculoskeletal disease characterized by the progressive loss of skeletal muscle mass, strength, and physical performance, presents significant challenges to global public health due to its adverse effects on mobility, morbidity, mortality, and healthcare costs. This comprehensive review explores the intricate connections between sarcopenia and low birth weight (LBW), emphasizing the developmental origins of health and disease (DOHaD) hypothesis, inflammatory processes (inflammaging), mitochondrial dysfunction, circadian rhythm disruptions, epigenetic mechanisms, and genetic variations revealed through genome-wide studies (GWAS). A systematic search strategy was developed using PubMed to identify relevant English-language publications on sarcopenia, LBW, DOHaD, inflammaging, mitochondrial dysfunction, circadian disruption, epigenetic mechanisms, and GWAS. The publications consist of 46.2% reviews, 21.2% cohort studies, 4.8% systematic reviews, 1.9% cross-sectional studies, 13.4% animal studies, 4.8% genome-wide studies, 5.8% epigenome-wide studies, and 1.9% book chapters. The review identified key factors contributing to sarcopenia development, including the DOHaD hypothesis, LBW impact on muscle mass, inflammaging, mitochondrial dysfunction, the influence of clock genes, the role of epigenetic mechanisms, and genetic variations revealed through GWAS. The DOHaD theory suggests that LBW induces epigenetic alterations during foetal development, impacting long-term health outcomes, including the early onset of sarcopenia. LBW correlates with reduced muscle mass, grip strength, and lean body mass in adulthood, increasing the risk of sarcopenia. Chronic inflammation (inflammaging) and mitochondrial dysfunction contribute to sarcopenia, with LBW linked to increased oxidative stress and dysfunction. Disrupted circadian rhythms, regulated by genes such as BMAL1 and CLOCK, are associated with both LBW and sarcopenia, impacting lipid metabolism, muscle mass, and the ageing process. Early-life exposures, including LBW, induce epigenetic modifications like DNA methylation (DNAm) and histone changes, playing a pivotal role in sarcopenia development. Genome-wide studies have identified candidate genes and variants associated with lean body mass, muscle weakness, and sarcopenia, providing insights into genetic factors contributing to the disorder. LBW emerges as a potential early predictor of sarcopenia development, reflecting the impact of intrauterine exposures on long-term health outcomes. Understanding the complex interplay between LBW with inflammaging, mitochondrial dysfunction, circadian disruption, and epigenetic factors is essential for elucidating the pathogenesis of sarcopenia and developing targeted interventions. Future research on GWAS and the underlying mechanisms of LBW-associated sarcopenia is warranted to inform preventive strategies and improve public health outcomes.

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.

SuperAgers and centenarians, dynamics of healthy ageing with cognitive resilience

Graceful healthy ageing and extended longevity is the most desired goal for human race. The process of ageing is inevitable and has a profound impact on the gradual deterioration of our physiology and health since it triggers the onset of many chronic conditions like dementia, osteoporosis, diabetes, arthritis, cancer, and cardiovascular disease. However, some people who lived/live more than 100 years called 'Centenarians" and how do they achieve their extended lifespans are not completely understood. Studying these unknown factors of longevity is important not only to establish a longer human lifespan but also to manage and treat people with shortened lifespans suffering from age-related morbidities. Furthermore, older adults who maintain strong cognitive function are referred to as "SuperAgers" and may be resistant to risk factors linked to cognitive decline. Investigating the mechanisms underlying their cognitive resilience may contribute to the development of therapeutic strategies that support the preservation of cognitive function as people age. The key to a long, physically, and cognitively healthy life has been a mystery to scientists for ages. Developments in the medical sciences helps us to a better understanding of human physiological function and greater access to medical care has led us to an increase in life expectancy. Moreover, inheriting favorable genetic traits and adopting a healthy lifestyle play pivotal roles in promoting longer and healthier lives. Engaging in regular physical activity, maintaining a balanced diet, and avoiding harmful habits such as smoking contribute to overall well-being. The synergy between positive lifestyle choices, access to education, socio-economic factors, environmental determinants and genetic supremacy enhances the potential for a longer and healthier life. Our article aims to examine the factors associated with healthy ageing, particularly focusing on cognitive health in centenarians. We will also be discussing different aspects of ageing including genomic instability, metabolic burden, oxidative stress and inflammation, mitochondrial dysfunction, cellular senescence, immunosenescence, and sarcopenia.

Frontiers in sarcopenia: Advancements in diagnostics, molecular mechanisms, and therapeutic strategies

The onset of sarcopenia is intimately linked with aging, posing significant implications not only for individual patient quality of life but also for the broader societal healthcare framework. Early and accurate identification of sarcopenia and a comprehensive understanding of its mechanistic underpinnings and therapeutic targets paramount to addressing this condition effectively. This review endeavors to present a cohesive overview of recent advancements in sarcopenia research and diagnosis. We initially delve into the contemporary diagnostic criteria, specifically referencing the European Working Group on Sarcopenia in Older People (EWGSOP) 2 and Asian Working Group on Sarcopenia (AWGS) 2019 benchmarks. Additionally, we elucidate comprehensive assessment techniques for muscle strength, quantity, and physical performance, highlighting tools such as grip strength, chair stand test, dual-energy X-ray Absorptiometry (DEXA), bioelectrical impedance analysis (BIA), gait speed, and short physical performance battery (SPPB), while also discussing their inherent advantages and limitations. Such diagnostic advancements pave the way for early identification and unequivocal diagnosis of sarcopenia. Proceeding further, we provide a deep-dive into sarcopenia's pathogenesis, offering a thorough examination of associated signaling pathways like the Myostatin, AMP-activated protein kinase (AMPK), insulin/IGF-1 Signaling (IIS), and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways. Each pathway's role in sarcopenia mediation is detailed, underscoring potential therapeutic target avenues. From a mechanistic perspective, the review also underscores the pivotal role of mitochondrial dysfunction in sarcopenia, emphasizing elements such as mitochondrial oxidative overload, mitochondrial biogenesis, and mitophagy, and highlighting their therapeutic significance. At last, we capture recent strides made in sarcopenia treatment, ranging from nutritional and exercise interventions to potential pharmacological and supplementation strategies. In sum, this review meticulously synthesizes the latest scientific developments in sarcopenia, aiming to enhance diagnostic precision in clinical practice and provide comprehensive insights into refined mechanistic targets and innovative therapeutic interventions, ultimately contributing to optimized patient care and advancements in the field.

Prognostic utility of paraspinal muscle index in elderly patients with community-acquired pneumonia

OBJECTIVE

This study investigated the associations between paraspinal muscle measurements on chest computed tomography and clinical outcomes of elderly patients with community-acquired pneumonia (CAP).

METHODS

This single-center, retrospective, observational study analyzed elderly patients (≥65 years) with CAP hospitalized through an emergency department between March 2020 and December 2022. We collected their baseline characteristics and laboratory data at the time of admission. The paraspinal muscle index and attenuation were calculated at the level of the 12th thoracic vertebra using chest computed tomography taken within 48 hours before or after admission. Univariable and multivariable logistic regression analyses were conducted to evaluate the association between paraspinal muscle measurements and 28-day mortality. Receiver operating characteristic (ROC) curve and area under the curve (AUC) analyses were used to evaluate the prognostic predictive power.

RESULTS

Of the 338 enrolled patients, 60 (17.8%) died within 28 days after admission. A high paraspinal muscle index was associated with low 28-day mortality in elderly patients with CAP (adjusted odds ratio, 0.994; 95% confidence interval, 0.992-0.997). The area under the ROC curve for the muscle index was 0.75, which outperformed the pneumonia severity index and the CURB-65 (confusion, urea, respiratory rate, blood pressure, age ≥65 years) metric, both of which showed an AUC of 0.64 in predicting mortality.

CONCLUSION

A high paraspinal muscle index was associated with low 28-day mortality in patients aged 65 years or older with CAP.

Effectiveness of resistance training in modulating inflammatory biomarkers among Asian patients with sarcopenia: a systematic review and meta-analysis of randomized controlled trials

Objective

Given the high incidence of sarcopenia among Asians, it is imperative to identify appropriate intervention methods. The International Clinical Practice Guidelines for Sarcopenia, developed by the International Conference on Sarcopenia and Frailty Research (ICFSR) task force, recommends resistance training (RT) as a primary treatment for managing sarcopenia. Inflammatory biomarkers serve as indicators of sarcopenia. However, there is currently insufficient conclusive evidence regarding the effectiveness of RT in modulating inflammatory biomarker levels among Asian participants with sarcopenia.

Data sources

Four databases were utilized for this study until October 9, 2023. This study focused on randomized controlled trials (RCTs) that examined the effects of RT on interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), and interleukin-10 (IL-10) about sarcopenia. This study has been registered in the PROSPERO database (CRD42024501855).

Results

The meta-analysis included six studies from Asians involving 278 participants. The results showed a significant decrease in RT for IL-6 (weighted mean difference (WMD) = -0.73, 95% confidence interval (CI) = -1.02 to -0.44; n=5). However, no significant differences were found for TNF-α (WMD = -1.00, 95% CI = -2.47 to 0.46; n=5), CRP (WMD = -0.45, 95% CI = -1.14 to 0.23; n=3), and IL-10 (WMD = 0.13, 95% CI = -3.99 to 4.25; n=2). Subgroup analysis revealed that factors including gender selection, intervention methods, frequency, period, and duration could have a particular effect on the part of inflammatory biomarkers.

Conclusion

RT has been shown to reduce part of the level of inflammatory markers, specifically IL-6, in Asian sarcopenia participants. However, other inflammatory factors, such as TNF-α, CRP, and IL-10, did not show significant changes. Further research should confirm the impact of RT on these indicators and explore the potential effects of various factors on different inflammatory markers, such as diet, body composition, and medications.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=501855, identifier CRD42024501855.

Associations between blood manganese levels and sarcopenia in adults: insights from the National Health and Nutrition Examination Survey

Background

While increasing concerns arise about the health effects of environmental pollutants, the relationship between blood manganese (Mn) and sarcopenia has yet to be fully explored in the general population.

Objective

This study aims to investigate the association between blood manganese (Mn) levels and sarcopenia in adults.

Methods

In our study, we evaluated 8,135 individuals aged 18-59 years, utilizing data from the National Health and Nutrition Examination Survey (NHANES) spanning 2011 to 2018. We employed generalized additive model (GAM) to discern potential non-linear relationships and utilized the two-piecewise linear regression model to probe the association between blood Mn levels and sarcopenia.

Results

After adjusting for potential confounders, we identified non-linear association between blood Mn levels and sarcopenia, with an inflection point at 13.45 μg/L. The effect sizes and the confidence intervals on the left and right sides of the inflection point were 1.006 (0.996 to 1.048) and 1.082 (1.043 to 1.122), respectively. Subgroup analysis showed that the effect sizes of blood Mn on sarcopenia have significant differences in gender and different BMI groups.

Conclusion

Our results showed that a reverse U-shaped curve between blood Mn levels and sarcopenia, with an identified the inflection point at blood Mn level of 13.45 μg/L.

Lower heart rate variability is associated with loss of muscle mass and sarcopenia in community-dwelling older Chinese adults

BACKGROUND/PURPOSE

Autonomic nervous system (ANS) disorders may occur in skeletal muscle disease, but the link between them has not been fully established. Studying the relationship between them may yield insights into the mechanisms and treatment of disease. This study aimed to explore the association between heart rate variability (HRV), sarcopenia, and subscales of sarcopenia (muscle mass, muscle strength, and physical mobility).

METHODS

2514 community-dwelling older Chinese participants were included in this study. The Asian Working Group for Sarcopenia guidelines were used to define sarcopenia. HRV was measured by 90-s electrocardiogram RR interval data. All HRV parameters were transformed using natural logarithms. Multiple regression analysis and multivariate linear regression was performed using potential correlates.

RESULTS

The overall prevalence of sarcopenia was 15.1 % (18.5 % in males and 12.6 % in females). In the logistic regression analysis model, there was a significant association between log-transformed standard deviation of RR interval (lnSDNN) (OR = 0.736, p = 0.019), log-transformed coefficient of variation of RR intervals (lnCVRR) (OR = 0.751, p = 0.020), log-transformed low-frequency power (lnLF) (OR = 0.861, p = 0.008), log-transformed high-frequency power (lnHF) (OR = 0.864, p = 0.003) and sarcopenia in the general population after adjusting for age, sex, body mass index (BMI), daily activity levels, hypertension, heart disease and cardiac drugs. In addition, in multivariate linear regression, lnSDNN (β = 0.146, p = 0.001), lnCVRR (β = 0.120, p = 0.010), lnLF (β = 0.066, p = 0.002) and lnHF (β = 0.065, p < 0.001) remained significantly positively associated with muscle mass, but there were no significant differences in grip strength and walking speed.

CONCLUSION

Sarcopenia was independently associated with lower heart rate variability in a community-dwelling elderly Chinese population. In addition, muscle mass was positively associated with heart rate variability in the elderly.

MFN2 overexpression in skeletal muscles of young and old mice causes a mild hypertrophy without altering mitochondrial respiration and H2O2 emission

AIM

Sarcopenia, the aging-related loss of muscle mass and function, is a debilitating process negatively impacting the quality of life of affected individuals. Although the mechanisms underlying sarcopenia are incompletely understood, impairments in mitochondrial dynamics, including mitochondrial fusion, have been proposed as a contributing factor. However, the potential of upregulating mitochondrial fusion proteins to alleviate the effects of aging on skeletal muscles remains unexplored. We therefore hypothesized that overexpressing Mitofusin 2 (MFN2) in skeletal muscle in vivo would mitigate the effects of aging on muscle mass and improve mitochondrial function.

METHODS

MFN2 was overexpressed in young (7 mo) and old (24 mo) male mice for 4 months through intramuscular injections of an adeno-associated viruses. The impacts of MFN2 overexpression on muscle mass and fiber size (histology), mitochondrial respiration, and H2O2 emission (Oroboros fluororespirometry), and various signaling pathways (qPCR and western blotting) were investigated.

RESULTS

MFN2 overexpression increased muscle mass and fiber size in both young and old mice. No sign of fibrosis, necrosis, or inflammation was found upon MFN2 overexpression, indicating that the hypertrophy triggered by MFN2 overexpression was not pathological. MFN2 overexpression even reduced the proportion of fibers with central nuclei in old muscles. Importantly, MFN2 overexpression had no impact on muscle mitochondrial respiration and H2O2 emission in both young and old mice. MFN2 overexpression attenuated the increase in markers of impaired autophagy in old muscles.

CONCLUSION

MFN2 overexpression may be a viable approach to mitigate aging-related muscle atrophy and may have applications for other muscle disorders.

Creatine supplementation for optimization of physical function in the patient at risk of functional disability: A systematic review and meta-analysis

BACKGROUND

The efficacy of creatine replacement through supplementation for the optimization of physical function in the population at risk of functional disability is unclear.

METHODS

We conducted a systematic literature search of MEDLINE, EMBASE, the Cochrane Library, and CINAHL from inception to November 2022. Studies included were randomized controlled trials (RCTs) comparing creatine supplementation with placebos in older adults and adults with chronic disease. The primary outcome was physical function measured by the sit-to-stand test after pooling data using random-effects modeling. We also performed a Bayesian meta-analysis to describe the treatment effect in probability terms. Secondary outcomes included other measures of physical function, muscle function, and body composition. The risk of bias was assessed using the Cochrane risk-of-bias tool.

RESULTS

We identified 33 RCTs, comprising 1076 participants. From six trials reporting the primary outcome, the pooled standardized mean difference (SMD) was 0.51 (95% confidence interval [CI]: 0.01-1.00; I2 = 62%; P = 0.04); using weakly informative priors, the posterior probability that creatine supplementation improves physical function was 66.7%. Upper-body muscle strength (SMD: 0.25; 95% CI: 0.06-0.44; I2 = 0%; P = 0.01), handgrip strength (SMD 0.23; 95% CI: 0.01-0.45; I2 = 0%; P = 0.04), and lean tissue mass (MD 1.08 kg; 95% CI: 0.77-1.38; I2 = 26%; P < 0.01) improved with creatine supplementation. The quality of evidence for all outcomes was low or very low because of a high risk of bias.

CONCLUSION

Creatine supplementation improves sit-to-stand performance, muscle function, and lean tissue mass. It is crucial to conduct high-quality prospective RCTs to confirm these hypotheses (PROSPERO number, CRD42023354929).

Mitochondrial Transplantation's Role in Rodent Skeletal Muscle Bioenergetics: Recharging the Engine of Aging

BACKGROUND

Mitochondria are the 'powerhouses of cells' and progressive mitochondrial dysfunction is a hallmark of aging in skeletal muscle. Although different forms of exercise modality appear to be beneficial to attenuate aging-induced mitochondrial dysfunction, it presupposes that the individual has a requisite level of mobility. Moreover, non-exercise alternatives (i.e., nutraceuticals or pharmacological agents) to improve skeletal muscle bioenergetics require time to be effective in the target tissue and have another limitation in that they act systemically and not locally where needed. Mitochondrial transplantation represents a novel directed therapy designed to enhance energy production of tissues impacted by defective mitochondria. To date, no studies have used mitochondrial transplantation as an intervention to attenuate aging-induced skeletal muscle mitochondrial dysfunction. The purpose of this investigation, therefore, was to determine whether mitochondrial transplantation can enhance skeletal muscle bioenergetics in an aging rodent model. We hypothesized that mitochondrial transplantation would result in sustained skeletal muscle bioenergetics leading to improved functional capacity.

METHODS

Fifteen female mice (24 months old) were randomized into two groups (placebo or mitochondrial transplantation). Isolated mitochondria from a donor mouse of the same sex and age were transplanted into the hindlimb muscles of recipient mice (quadriceps femoris, tibialis anterior, and gastrocnemius complex).

RESULTS

The results indicated significant increases (ranging between ~36% and ~65%) in basal cytochrome c oxidase and citrate synthase activity as well as ATP levels in mice receiving mitochondrial transplantation relative to the placebo. Moreover, there were significant increases (approx. two-fold) in protein expression of mitochondrial markers in both glycolytic and oxidative muscles. These enhancements in the muscle translated to significant improvements in exercise tolerance.

CONCLUSIONS

This study provides initial evidence showing how mitochondrial transplantation can promote skeletal muscle bioenergetics in an aging rodent model.

Association between the oxidative balance score and low muscle mass in middle-aged US adults

Background

Oxidative Balance Score (OBS) is a tool for assessing the oxidative stress-related exposures of diet and lifestyle. The study aimed to investigate the association between OBS and low muscle mass.

Methods

Overall, 6,307 individuals over the age of 18 were assessed using data from the 2011 to 2018 National Health and Nutrition Examination Survey (NHANES). Weighted logistic regression and models were used, together with adjusted models.

Results

There was a negative relationship between OBS and low muscle mass [odds ratio (OR): 0.96, 95% confidence interval (CI): 0.94-0.97, p< 0.0001] using the first OBS level as reference. The values (all 95% CI) were 0.745 (0.527-1.054) for the second level, 0.650 (0.456-0.927) for the third level, and 0.326 (0.206-0.514) for the fourth level (P for trend <0.0001). Independent links with low muscle mass were found for diet and lifestyle factors. A restricted cubic spline model indicated a non-linear association between OBS and low muscle mass risk (P for non-linearity<0.05). In addition, the inflection points of the nonlinear curves for the relationship between OBS and risk of low muscle mass were 20.

Conclusion

OBS and low muscle mass were found to be significantly negatively correlated. By modulating oxidative balance, a healthy lifestyle and antioxidant rich diet could be a preventive strategy for low muscle mass.

Effect of resistance training plus enriched probiotic supplement on sestrin2, oxidative stress, and mitophagy markers in elderly male Wistar rats

This study aimed to determine the effects of resistance training combined with a probiotic supplement enriched with vitamin D and leucine on sestrin2, oxidative stress, antioxidant defense, and mitophagy markers in aged Wistar rats. Thirty-five male rats were randomly assigned to two age groups (old with 18-24 months of age and young with 8-12 weeks of age) and then divided into five groups, including (1) old control (OC: n = 5 + 2 for reserve in all groups), (2) young control (YC: n = 5), (3) old resistance training (OR: n = 5), (4) old resistance training plus supplement (ORS: n = 5), and old supplement group (OS: n = 5). Training groups performed ladder climbing resistance training 3 times per week for 8 weeks. Training intensity was inserted progressively, with values equal to 65, 75, and 85, determining rats' maximal carrying load capacity. Each animal made 5 to 8 climbs in each training session, and the time of each climb was between 12 and 15 s, although the time was not the subject of the evaluation, and the climbing pattern was different in the animals. Old resistance plus supplement and old supplement groups received 1 ml of supplement 5 times per week by oral gavage in addition to standard feeding, 1 to 2 h post training sessions. Forty-eight hours after the end of the training program, 3 ml of blood samples were taken, and all rats were then sacrificed to achieve muscle samples. After 8 weeks of training, total antioxidant capacity and superoxide dismutase activity levels increased in both interventions. A synergistic effect of supplement with resistance training was observed for total antioxidant capacity, superoxide dismutase, and PTEN-induced kinase 1. Sestrin 2 decreased in intervention groups. These results suggest that resistance training plus supplement can boost antioxidant defense and mitophagy while potentially decreasing muscle strength loss.

The Effect of Glycine and N-Acetylcysteine on Oxidative Stress in the Spinal Cord and Skeletal Muscle After Spinal Cord Injury

Oxidative stress is a frequently occurring pathophysiological feature of spinal cord injury (SCI) and can result in secondary injury to the spinal cord and skeletal muscle atrophy. Studies have reported that glycine and N-acetylcysteine (GlyNAC) have anti-aging and anti-oxidative stress properties; however, to date, no study has assessed the effect of GlyNAC in the treatment of SCI. In the present work, we established a rat model of SCI and then administered GlyNAC to the animals by gavage at a dose of 200 mg/kg for four consecutive weeks. The BBB scores of the rats were significantly elevated from the first to the eighth week after GlyNAC intervention, suggesting that GlyNAC promoted the recovery of motor function; it also promoted the significant recovery of body weight of the rats. Meanwhile, the 4-week heat pain results also suggested that GlyNAC intervention could promote the recovery of sensory function in rats to some extent. Additionally, after 4 weeks, the levels of glutathione and superoxide dismutase in spinal cord tissues were significantly elevated, whereas that of malondialdehyde was significantly decreased in GlyNAC-treated animals. The gastrocnemius wet weight ratio and total antioxidant capacity were also significantly increased. After 8 weeks, the malondialdehyde level had decreased significantly in spinal cord tissue, while reactive oxygen species accumulation in skeletal muscle had decreased. These findings suggested that GlyNAC can protect spinal cord tissue, delay skeletal muscle atrophy, and promote functional recovery in rats after SCI.

The efferocytosis process in aging: Supporting evidence, mechanisms, and therapeutic prospects for age-related diseases

BACKGROUND

Aging is characterized by an ongoing struggle between the buildup of damage caused by a combination of external and internal factors. Aging has different effects on phagocytes, including impaired efferocytosis. A deficiency in efferocytosis can cause chronic inflammation, aging, and several other clinical disorders.

AIM OF REVIEW

Our review underscores the possible feasibility and extensive scope of employing dual targets in various age-related diseases to reduce the occurrence and progression of age-related diseases, ultimately fostering healthy aging and increasing lifespan. Key scientific concepts of review Hence, the concurrent implementation of strategies aimed at augmenting efferocytic mechanisms and anti-aging treatments has the potential to serve as a potent intervention for extending the duration of a healthy lifespan. In this review, we comprehensively discuss the concept and physiological effects of efferocytosis. Subsequently, we investigated the association between efferocytosis and the hallmarks of aging. Finally, we discuss growing evidence regarding therapeutic interventions for age-related disorders, focusing on the physiological processes of aging and efferocytosis.

Mitochondrial involvement in sarcopenia

Sarcopenia lowers the quality-of-life for millions of people across the world, as accelerated loss of skeletal muscle mass and function contributes to both age- and disease-related frailty. Physical activity remains the only proven therapy for sarcopenia to date, but alternatives are much sought after to manage this progressive muscle disorder in individuals who are unable to exercise. Mitochondria have been widely implicated in the etiology of sarcopenia and are increasingly suggested as attractive therapeutic targets to help restore the perturbed balance between protein synthesis and breakdown that underpins skeletal muscle atrophy. Reviewing current literature, we note that mitochondrial bioenergetic changes in sarcopenia are generally interpreted as intrinsic dysfunction that renders muscle cells incapable of making sufficient ATP to fuel protein synthesis. Based on the reported mitochondrial effects of therapeutic interventions, however, we argue that the observed bioenergetic changes may instead reflect an adaptation to pathologically decreased energy expenditure in sarcopenic muscle. Discrimination between these mechanistic possibilities will be crucial for improving the management of sarcopenia.

Identifying Acss1, Mtfp1 and Oxct1 as key regulators and promising biomarkers of sarcopenia in various models

Mitochondrial dysfunction plays a critical role in muscular homeostasis, but the molecular mechanism underlying mitochondrial dynamics and sarcopenia awaits to be uncovered. We all know that malnutrition, cachexia, and type 2 diabetes are significant contributors to the development of sarcopenia.Therefore, we analyzed a bioinformatic analysis on cathectic differentially expressed genes (cDEGs), fasted differentially genes (fDEGs) and mitochondria-related genes. The overlapping genes identified were then validated by RT-qPCR and Western blotting experiments in various sarcopenia mice models and used to predict aging-related muscle loss in humans. First, the correlation analysis and PPI network indicated 6 overlapping candidates (Bdh1, Gdap1, Acss1, Mtfp1, Idh2, Oxct1) may constitute a regulatory effect in mitochondrial dynamics and muscle wasting. Next, we successfully established fasted, Lewis lung carcinoma (LLC) and Diabetes Mellitus (DM) induced sarcopenia mice models and verified that Acss1, Mtfp1 and Oxct1 shared common and significant variation tendency in these sarcopenia mice models. Further-more, Pearson correlation analysis showed that Acss1 was negatively related to the weight of gastrocnemius while Mtfp1 and Oxct1 displayed a significantly positive correlation with gastrocnemius weight in sarcopenic mice model induced by LLC, fasting and DM. What's more, ROC analysis based on human aging-related datasets indicated Acss1, Mtfp1, Oxct1 had outstanding diagnostic capabilities for sarcopenia. In general, we identified three hub genes (Acss1, Mtfp1 and Oxct1) that are strongly associated with mitochondrial dysfunction in sarcopenia and may provide novel and reliable indicators for screening, diagnosis, and prognosis, as well as potential therapeutic targets for patients with sarcopenia.

5'-Cytimidine Monophosphate Ameliorates H2O2-Induced Muscular Atrophy in C2C12 Myotubes by Activating IRS-1/Akt/S6K Pathway

Age-related muscle atrophy (sarcopenia), characterized by reduced skeletal muscle mass and muscle strength, is becoming increasingly prevalent worldwide, which is especially true for older people, and can seriously damage health and quality of life in older adults. This study aims to investigate the beneficial effects of 5'-cytimidine monophosphate (CMP) on H2O2-induced muscular atrophy in C2C12 myotubes. C2C12 myotubes were treated with H2O2 in the presence and absence of CMP and the changes in the anti-oxidation, mitochondrial functions, and expression of sarcopenia-related proteins were observed. Immunofluorescence analysis showed that CMP significantly increased the diameter of myotubes. We found that CMP could increase the activity of antioxidant enzymes and improve mitochondrial dysfunction, as well as reduce inflammatory cytokine levels associated with sarcopenia. RNA-seq analysis showed that CMP could relieve insulin resistance and promote protein digestion and absorption. Western blot analysis further confirmed that CMP could promote the activation of the IRS-1/Akt/S6K signaling pathway and decrease the expression of MuRF1 and Atrogin-1, which are important markers of muscle atrophy. The above results suggest that CMP protects myotubes from H2O2-induced atrophy and that its potential mechanism is associated with activating the IRS-1/Akt/S6K pathway to promote protein synthesis by improving mitochondrial dysfunction and insulin resistance. These results indicate that CMP can improve aging-related sarcopenia.

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.

Blockade of angiotensin II modulates insulin-like growth factor 1-mediated skeletal muscle homeostasis in experimental steatohepatitis

Sarcopenia is associated with mortality in patients with nonalcoholic steatohepatitis (NASH). Angiotensin II receptor blocker (ARB) has been suggested to prevent sarcopenia, but reports on its effect on NASH-derived skeletal muscle atrophy in conjunction with insulin-like growth factor 1 (IGF-1)-mediated muscle homeostasis are few. Our aim was to examine the combined effect of the ARB losartan and IGF-1 replacement on skeletal muscle atrophy in a methionine-choline deficient (MCD) diet-fed murine steatohepatitis model. The MCD-fed mice developed steatohepatitis and skeletal muscle atrophy, as indicated by the reduction of psoas muscle mass and attenuation of forelimb and hindlimb grip strength. Significantly suppressed steatohepatitis and skeletal muscle atrophy was observed after single treatment with ARB or IGF-1, and these effects were augmented after combination treatment. Treatment with ARB and IGF-1 effectively inhibited ubiquitin proteasome-mediated protein degradation by reducing forkhead box protein O1 (FOXO1) and FOXO3a transcriptional activity in the skeletal muscle. Combined ARB and IGF-1 decreased the intramuscular expression of proinflammatory cytokines (i.e., TNFα, IL6, and IL1β) and increased the Trolox equivalent antioxidant capacity and antioxidant enzymes (CAT, GPX1, SOD2, and CYTB). This antioxidant effect was based on downregulation of NADPH oxidase (NOX) 2, normalization of mitochondrial biogenesis and dynamics. Moreover, ARB increased the hepatic and plasma IGF-1 levels and improved steatohepatitis, leading to enhanced skeletal muscle protein synthesis mediated by IGF-1/ AKT/ mechanistic target of rapamycin signaling. Collectively, combined ARB and IGF-1 replacement could be a promising new therapeutic target for NASH-derived skeletal muscle wasting.

Passive exercise is an effective alternative to HRT for restoring OVX induced mitochondrial dysfunction in skeletal muscle

Background

Postmenopausal women are more prone to develop muscle weakness, which is strongly associated with impairment of mitochondrial function in skeletal muscle. This study aimed to examine the impact of a passive exercise modality, whole-body vibration training (WBVT), on muscle mitochondrial function in ovariectomized (OVX) mice, in comparison with 17β-estradiol (E2) replacement.

Methods

Female C57BL/6J mice were assigned to four groups: sham operation control group (Sham), ovariectomized group (OVX), OVX with E2 supplement group (OVX+E), and OVX with WBVT group (OVX+W). The estrous cycle, body weight, body composition, and muscle strength of the mice were monitored after the operation. Serum E2 level was assessed by enzyme-linked immunosorbent assay (ELISA). The ATP levels were determined using a luciferase-catalyzed bioluminescence assay. The activity of mitochondrial respiration chain complexes was evaluated using high-resolution respirometry (O2K). Expression levels of oxidative phosphorylation (OXPHOS), peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), and mitochondrial transcription factor A (TFAM) were detected using western blotting.

Results

We observed decreased muscle strength and impaired mitochondrial function in the skeletal muscle of OVX mice. The vibration training alleviated these impairments as much as the E2 supplement. In addition, the vibration training was superior to the ovariectomy and the estradiol replacement regarding the protein expression of PGC-1α and TFAM.

Conclusion

WBVT improves the OVX-induced decline in muscle strength and impairment of mitochondrial function in the skeletal muscle. This passive exercise strategy may be useful as an alternative to E2 replacement for preventing menopausal muscular weakness. Further studies are needed to understand the effects of WBVT on various physiological systems, and precautions should be taken when implementing it in patient treatment.

The Impact of 5-Aminolevulinic Acid Supplementation on Redox Balance and Aerobic Capacity

We examined the impact of 5-aminolevulinic acid (5-ALA) and sodium-ferrous-citrate supplementation on aerobic capacity and redox balance through a placebo-controlled, double-blind trial. Fourteen healthy volunteers were randomly assigned to Pla + ALA (4-week placebo followed by 4-week 5-ALA supplementation) or ALA + Pla (4-week 5-ALA supplement followed by a 4-week placebo) group and administered 5-ALA (25 mg/day) or placebo once daily. The participants underwent submaximal incremental cycling tests at weeks 0, 2, 4, 6, and 8. In the cycling test at week 0, individual load-intensity stages required for blood lactate levels >2 mmol/L (lactate threshold, LT) and 4 mmol/L (onset of blood lactate accumulation, OBLA) were determined. The heart rate (HR), blood lactate (La), and oxidative stress markers (diacron reactive oxygen metabolite, d-ROMs; biological antioxidant potential, BAP) were measured at resting, LT, and OBLA states in each cycling test. Marker values were not significantly different between the groups. HR, La, and d-ROMs at resting, LT, and OBLA states were not significantly different among the conditions. BAP and BAP/d-ROMs ratios were significantly different in the OBLA state at week 4 of the 5-ALA group compared with that of the placebo group (p < 0.05). In conclusion, 5-ALA supplementation might improve redox balance during high-intensity aerobic exercise.

Modulation of mitochondrial activity by sugarcane (Saccharum officinarum L.) top extract and its bioactive polyphenols: a comprehensive transcriptomics analysis in C2C12 myotubes and HepG2 hepatocytes

Age-related mitochondrial dysfunction leads to defects in cellular energy metabolism and oxidative stress defense systems, which can contribute to tissue damage and disease development. Among the key regulators responsible for mitochondrial quality control, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is an important target for mitochondrial dysfunction. We have previously reported that bioactive polyphenols extracted from sugarcane top (ST) ethanol extract (STEE) could activate neuronal energy metabolism and increase astrocyte PGC-1α transcript levels. However, their potential impact on the mitochondria activity in muscle and liver cells has not yet been investigated. To address this gap, our current study examined the effects of STEE and its polyphenols on cultured myotubes and hepatocytes in vitro. Rhodamine 123 assay revealed that the treatment with STEE and its polyphenols resulted in an increase in mitochondrial membrane potential in C2C12 myotubes. Furthermore, a comprehensive examination of gene expression patterns through transcriptome-wide microarray analysis indicated that STEE altered gene expressions related to mitochondrial functions, fatty acid metabolism, inflammatory cytokines, mitogen-activated protein kinase (MAPK) signaling, and cAMP signaling in both C2C12 myotubes and HepG2 hepatocytes. Additionally, protein-protein interaction analysis identified the PGC-1α interactive-transcription factors-targeted regulatory network of the genes regulated by STEE, and the quantitative polymerase chain reaction results confirmed that STEE and its polyphenols upregulated the transcript levels of PGC-1α in both C2C12 and HepG2 cells. These findings collectively suggest the potential beneficial effects of STEE on muscle and liver tissues and offer novel insights into the potential nutraceutical applications of this material.

Ashwagandha Ethanol Extract Attenuates Sarcopenia-Related Muscle Atrophy in Aged Mice

The investigation focused on the impact of Withania somnifera (ashwagandha) extract (WSE) on age-related mechanisms affecting skeletal muscle sarcopenia-related muscle atrophy in aged mice. Beyond evaluating muscular aspects, the study explored chronic low-grade inflammation, muscle regeneration, and mitochondrial biogenesis. WSE administration, in comparison to the control group, demonstrated no significant differences in body weight, diet, or water intake, affirming its safety profile. Notably, WSE exhibited a propensity to reduce epidermal and abdominal fat while significantly increasing muscle mass at a dosage of 200 mg/kg. The muscle-to-fat ratio, adjusted for body weight, increased across all treatment groups. WSE administration led to a reduction in the pro-inflammatory cytokines TNF-α and IL-1β, mitigating inflammation-associated muscle atrophy. In a 12-month-old mouse model equivalent to a 50-year-old human, WSE effectively preserved muscle strength, stabilized grip strength, and increased muscle tissue weight. Positive effects were observed in running performance and endurance. Mechanistically, WSE balanced muscle protein synthesis/degradation, promoted fiber differentiation, and enhanced mitochondrial biogenesis through the IGF-1/Akt/mTOR pathway. This study provides compelling evidence for the anti-sarcopenic effects of WSE, positioning it as a promising candidate for preventing sarcopenia pending further clinical validation.

Pulmonary hypertension alters blood flow distribution and impairs the hyperemic response in the rat diaphragm

Pulmonary hypertension (PH) is characterized by pulmonary vascular remodeling, respiratory muscle and cardiac impairments, and exercise intolerance. Specifically, impaired gas exchange increases work of the diaphragm; however, compromised contractile function precludes the diaphragm from meeting the increased metabolic demand of chronic hyperventilation in PH. Given that muscle contractile function is in part, dependent upon adequate blood flow (Q ˙ ), diaphragmatic dysfunction may be predicated by an inability to match oxygen delivery with oxygen demand. We hypothesized that PH rats would demonstrate a decreased hyperemic response to contractions compared to healthy controls. Methods: Sprague-Dawley rats were randomized into healthy (HC, n = 7) or PH (n = 7) groups. PH rats were administered monocrotaline (MCT) while HC rats received vehicle. Disease progression was monitored via echocardiography. Regional and total diaphragm blood flow and vascular conductance at baseline and during 3 min of electrically-stimulated contractions were determined using fluorescent microspheres. Results: PH rats displayed morphometric and echocardiographic criteria for disease (i.e., acceleration time/ejection time, right ventricular hypertrophy). In all rats, total costal diaphragm Q ˙ increased during contractions and did not differ between groups. In HC rats, there was a greater increase in medial costal Q ˙ compared to PH rats (55% ± 3% vs. 44% ± 4%, p < 0.05), who demonstrated a redistribution of Q ˙ to the ventral costal region. Conclusion: These findings support a redistribution of regional diaphragm perfusion and an impaired medial costal hyperemic response in PH, suggesting that PH alters diaphragm vascular function and oxygen delivery, providing a potential mechanism for PH-induced diaphragm contractile dysfunction.

The mediating role of inflammaging between mitochondrial dysfunction and sarcopenia in aging: a review

Sarcopenia, characterized by the insidious reduction of skeletal muscle mass and strength, detrimentally affects the quality of life in elderly cohorts. Present therapeutic strategies are confined to physiotherapeutic interventions, signaling a critical need for elucidation of the etiological underpinnings to facilitate the development of innovative pharmacotherapies. Recent scientific inquiries have associated mitochondrial dysfunction and inflammation with the etiology of sarcopenia. Mitochondria are integral to numerous fundamental cellular processes within muscle tissue, including but not limited to apoptosis, autophagy, signaling via reactive oxygen species, and the maintenance of protein equilibrium. Deviations in mitochondrial dynamics, coupled with compromised oxidative capabilities, autophagic processes, and protein equilibrium, result in disturbances to muscular architecture and functionality. Mitochondrial dysfunction is particularly detrimental as it diminishes oxidative phosphorylation, escalates apoptotic activity, and hinders calcium homeostasis within muscle cells. Additionally, deleterious feedback loops of deteriorated respiration, exacerbated oxidative injury, and diminished quality control mechanisms precipitate the acceleration of muscular senescence. Notably, mitochondria exhibiting deficient energetic metabolism are pivotal in precipitating the shift from normative muscle aging to a pathogenic state. This analytical review meticulously examines the complex interplay between mitochondrial dysfunction, persistent inflammation, and the pathogenesis of sarcopenia. It underscores the imperative to alleviate inflammation and amend mitochondrial anomalies within geriatric populations as a strategy to forestall and manage sarcopenia. An initial overview provides a succinct exposition of sarcopenia and its clinical repercussions. The discourse then progresses to an examination of the direct correlation between mitochondrial dysfunction and the genesis of sarcopenia. Concomitantly, it accentuates potential synergistic effects between inflammatory responses and mitochondrial insufficiencies during the aging of skeletal muscle, thereby casting light upon emergent therapeutic objectives. In culmination, this review distills the prevailing comprehension of the mitochondrial and inflammatory pathways implicated in sarcopenia and delineates extant lacunae in knowledge to orient subsequent scientific inquiry.