The mechanisms and treatments for sarcopenia: could exosomes be a perspective research strategy in the future?

Dynapenia and sarcopenia identify walking speed decline in women but not in men

OBJECTIVE

To determine the best indicator of mobility decline between dynapenia, low skeletal muscle mass index (SMMI), and sarcopenia defined by the EWGSOP2 using different cutoff points for grip strength.

METHODS

A longitudinal study was conducted with a follow-up of eight years, involving 2,680 individuals aged 60 and older who participated in the ELSA study with a walking speed greater than 0.8 m/s at baseline. Dynapenia was defined using different cutoff points for grip strength. SMMI was defined by the 20th percentile of the entire ELSA sample distribution and sarcopenia was defined based on the EWGSOP2, using different cutoff points for grip strength. Mobility was analysed using the walking speed test.

RESULTS

Over time, the greatest decline in walking speed occurred in dynapenic women with grip strength < 17 kg (-0.005 m/s per year; 95 % CI: -0.01 to -0.001) and < 20 kg (-0.007 m/s per year; 95 % CI: -0.01 to -0.001). With regards to sarcopenia, the greatest walking speed decline occurred in women with probable sarcopenia when defined by grip strength < 17 kg [(-0.006 m/s per year; 95 % CI: -0.01 to -0.001) or grip strength < 20 kg (-0.007 m/s per year; 95 % CI: -0.01 to -0.001)]. Dynapenia in men as well as low SMMI and sarcopenia in men and women did not enable identifying the risk of mobility decline.

CONCLUSION

Dynapenia and probable sarcopenia defined by grip strength < 17 kg and < 20 kg enabled identifying walking speed decline over time only in women.

Proteomic profiling of human plasma extracellular vesicles identifies PF4 and C1R as novel biomarker in sarcopenia

BACKGROUND

Sarcopenia, the gradual and generalized loss of muscle mass and function with ageing, is one of the major health problems in older adults, given its high prevalence and substantial socioeconomic implications. Despite the extensive efforts to reach consensus on definition and diagnostic tests and cut-offs for sarcopenia, there is an urgent and unmet need for non-invasive, specific and sensitive biomarkers for the disease. Extracellular vesicles (EVs) are present in different biofluids including plasma, whose cargo reflects cellular physiology. This work analysed EV proteome in sarcopenia and robust patients in the search for differentially contained proteins that can be used to diagnose the disease.

METHODS

Plasma small EVs (sEVs) from a total of 29 robust controls (aged 73.4 ± 5.6 years; 11 men and 18 women) and 49 sarcopenic patients (aged 82.3 ± 5.4 years; 15 men and 34 women) aged 65 years and older were isolated and their cargo was analysed by proteomics. Proteins whose concentration in sEVs was different between sarcopenic and robust patients were further validated using ELISA. The concentration of these candidates was correlated to the EWGSOP2 sarcopenia tests for low muscle strength and low physical performance, and receiver operating characteristic (ROC) curve analyses were carried out to evaluate their diagnostic power, sensitivity and specificity.

RESULTS

Proteomic analysis identified 157 sEVs proteins in both sarcopenic and robust samples. Among them, 48 proteins had never been reported in the ExoCarta nor Vesiclepedia databases. Statistical analysis revealed eight proteins whose concentration was significantly different between groups: PF4 (log2 FC = 4.806), OIT3 (log2 FC = -1.161), MMRN1 (log2 FC = -1.982), MASP1 (log2 FC = -0.627), C1R (log2 FC = 1.830), SVEP1 (log2 FC = 1.295), VCAN (FC = 0.937) and SPTB (log2 FC = 1.243). Among them, platelet factor 4 (PF4) showed the lowest concentration while Complement C1r subcomponent (C1R) increased the most in sarcopenic patients, being these results confirmed by ELISA (P = 1.07E-09 and P = 0.001287, respectively). The concentrations of candidate proteins significantly correlated with EWGSOP2 tests currently used. ROC curve analysis showed an area under the curve of 0.8921 and 0.7476 for PF4 and C1R, respectively. Choosing the optimal for PF4, 80% sensitivity and 85.71% specificity was reached while the optimal cut-off value of C1R would allow sarcopenia diagnosis with 75% sensitivity and 66.67% specificity.

CONCLUSIONS

Our results support the determination of EV PF4 and C1R as plasma diagnostic biomarkers in sarcopenia and open the door to investigate the role of the content of these vesicles in the pathogeny of the disease.

Differential Responses to Aging Among the Transcriptome and Proteome of Mesenchymal Progenitor Populations

The biological aging of stem cells (exhaustion) is proposed to contribute to the development of a variety of age-related conditions. Despite this, little is understood about the specific mechanisms which drive this process. In this study, we assess the transcriptomic and proteomic changes in 3 different populations of mesenchymal progenitor cells from older (50-70 years) and younger (20-40 years) individuals to uncover potential mechanisms driving stem cell exhaustion in mesenchymal tissues. To do this, we harvested primary bone marrow mesenchymal stem and progenitor cells (MPCs), circulating osteoprogenitors (COP), and adipose-derived stem cells (ADSCs) from younger and older donors, with an equal number of samples from men and women. These samples underwent RNA sequencing and label-free proteomic analysis, comparing the younger samples to the older ones. There was a distinct transcriptomic phenotype in the analysis of pooled older stem cells, suggestive of suppressed proliferation and differentiation; however, these changes were not reflected in the proteome of the cells. Analyzed independently, older MPCs had a distinct phenotype in both the transcriptome and proteome consistent with altered differentiation and proliferation with a proinflammatory immune shift in older adults. COP cells showed a transcriptomic shift to proinflammatory signaling but no consistent proteomic phenotype. Similarly, ADSCs displayed transcriptomic shifts in physiologies associated with cell migration, adherence, and immune activation but no proteomic change with age. These results show that there are underlying transcriptomic changes with stem cell aging that may contribute to a decline in tissue regeneration. However, the proteome of the cells was inconsistently regulated.

Histone β-hydroxybutyrylation is critical in reversal of sarcopenia

Sarcopenia, a leading cause for global disability and mortality, is an age-related muscular disorder, characterized by accelerated muscle mass loss and functional decline. It is known that caloric restriction (CR), ketogenic diet or endurance exercise lessen sarcopenia and elevate circulating β-hydroxybutyrate (β-HB) levels. Whether the elevated β-HB is essential to the reversal of sarcopenia, however, remains unclear. Here we show in both Caenorhabditis elegans and mouse models that an increase of β-HB reverse myofiber atrophy and improves motor functions at advanced ages. β-HB-induced histone lysine β-hydroxybutyrylation (Kbhb) is indispensable for the reversal of sarcopenia. Histone Kbhb enhances transcription of genes associated with mitochondrial pathways, including oxidative phosphorylation, ATP metabolic process and aerobic respiration. This ultimately leads to improve mitochondrial integrity and enhance mitochondrial respiration. The histone Kbhb are validated in mouse model with CR. Thus, we demonstrate that β-HB induces histone Kbhb, increases mitochondrial function, and reverses 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.

Extracellular vesicles in cancer cachexia: deciphering pathogenic roles and exploring therapeutic horizons

Cancer cachexia (CC) is a debilitating syndrome that affects 50-80% of cancer patients, varying in incidence by cancer type and significantly diminishing their quality of life. This multifactorial syndrome is characterized by muscle and fat loss, systemic inflammation, and metabolic imbalance. Extracellular vesicles (EVs), including exosomes and microvesicles, play a crucial role in the progression of CC. These vesicles, produced by cancer cells and others within the tumor environment, facilitate intercellular communication by transferring proteins, lipids, and nucleic acids. A comprehensive review of the literature from databases such as PubMed, Scopus, and Web of Science reveals insights into the formation, release, and uptake of EVs in CC, underscoring their potential as diagnostic and prognostic biomarkers. The review also explores therapeutic strategies targeting EVs, which include modifying their release and content, utilizing them for drug delivery, genetically altering their contents, and inhibiting key cachexia pathways. Understanding the role of EVs in CC opens new avenues for diagnostic and therapeutic approaches, potentially mitigating the syndrome's impact on patient survival and quality of life.

Emerging Therapeutic Strategies in Sarcopenia: An Updated Review on Pathogenesis and Treatment Advances

Sarcopenia is a prevalent degenerative skeletal muscle condition in the elderly population, posing a tremendous burden on diseased individuals and healthcare systems worldwide. Conventionally, sarcopenia is currently managed through nutritional interventions, physical therapy, and lifestyle modification, with no pharmaceutical agents being approved for specific use in this disease. As the pathogenesis of sarcopenia is still poorly understood and there is no treatment recognized as universally effective, recent research efforts have been directed at better comprehending this illness and diversifying treatment strategies. In this respect, this paper overviews the new advances in sarcopenia treatment in correlation with its underlying mechanisms. Specifically, this review creates an updated framework for sarcopenia, describing its etiology, pathogenesis, risk factors, and conventional treatments, further discussing emerging therapeutic approaches like new drug formulations, drug delivery systems, stem cell therapies, and tissue-engineered scaffolds in more detail.

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.

Exosome-Mediated Impact on Systemic Metabolism

Exosomes are small extracellular vesicles that carry lipids, proteins, and microRNAs (miRNAs). They are released by all cell types and can be found not only in circulation but in many biological fluids. Exosomes are essential for interorgan communication because they can transfer their contents from donor to recipient cells, modulating cellular functions. The miRNA content of exosomes is responsible for most of their biological effects, and changes in exosomal miRNA levels can contribute to the progression or regression of metabolic diseases. As exosomal miRNAs are selectively sorted and packaged into exosomes, they can be useful as biomarkers for diagnosing diseases. The field of exosomes and metabolism is expanding rapidly, and researchers are consistently making new discoveries in this area. As a result, exosomes have great potential for a next-generation drug delivery platform for metabolic diseases.

The Current Landscape of Pharmacotherapies for Sarcopenia

Sarcopenia is a skeletal muscle disorder characterized by progressive and generalized decline in muscle mass and function. Although it is mostly known as an age-related disorder, it can also occur secondary to systemic diseases such as malignancy or organ failure. It has demonstrated a significant relationship with adverse outcomes, e.g., falls, disabilities, and even mortality. Several breakthroughs have been made to find a pharmaceutical therapy for sarcopenia over the years, and some have come up with promising findings. Yet still no drug has been approved for its treatment. The key factor that makes finding an effective pharmacotherapy so challenging is the general paradigm of standalone/single diseases, traditionally adopted in medicine. Today, it is well known that sarcopenia is a complex disorder caused by multiple factors, e.g., imbalance in protein turnover, satellite cell and mitochondrial dysfunction, hormonal changes, low-grade inflammation, senescence, anorexia of aging, and behavioral factors such as low physical activity. Therefore, pharmaceuticals, either alone or combined, that exhibit multiple actions on these factors simultaneously will likely be the drug of choice to manage sarcopenia. Among various drug options explored throughout the years, testosterone still has the most cumulated evidence regarding its effects on muscle health and its safety. A mas receptor agonist, BIO101, stands out as a recent promising pharmaceutical. In addition to the conventional strategies (i.e., nutritional support and physical exercise), therapeutics with multiple targets of action or combination of multiple therapeutics with different targets/modes of action appear to promise greater benefit for the prevention and treatment of sarcopenia.

Handelin alleviates cachexia- and aging-induced skeletal muscle atrophy by improving protein homeostasis and inhibiting inflammation

BACKGROUND

Handelin is a bioactive compound from Chrysanthemum indicum L. that improves motor function and muscle integrity during aging in Caenorhabditis elegans. This study aimed to further evaluate the protective effects and molecular mechanisms of handelin in a mouse muscle atrophy model induced by cachexia and aging.

METHODS

A tumour necrosis factor (TNF)-α-induced atrophy model was used to examine handelin activity in cultured C2C12 myotubes in vitro. Lipopolysaccharide (LPS)-treated 8-week-old model mice and 23-month-old (aged) mice were used to examine the therapeutic effects of handelin on cachexia- and aging-induced muscle atrophy, respectively, in vivo. Protein and mRNA expressions were analysed by Western blotting, ELISA and quantitative PCR, respectively. Skeletal muscle mass was measured by histological analysis.

RESULTS

Handelin treatment resulted in an upregulation of protein levels of early (MyoD and myogenin) and late (myosin heavy chain, MyHC) differentiation markers in C2C12 myotubes (P < 0.05), and enhanced mitochondrial respiratory (P < 0.05). In TNF-α-induced myotube atrophy model, handelin maintained MyHC protein levels, increased insulin-like growth factor (Igf1) mRNA expression and phosphorylated protein kinase B protein levels (P < 0.05). Handelin also reduced atrogin-1 expression, inhibited nuclear factor-κB activation and reduced mRNA levels of interleukin (Il)6, Il1b and chemokine ligand 1 (Cxcl1) (P < 0.05). In LPS-treated mice, handelin increased body weight (P < 0.05), the weight (P < 0.01) and cross-sectional area (CSA) of the soleus muscle (P < 0.0001) and improved motor function (P < 0.05). In aged mice, handelin slightly increased the weight of the tibialis anterior muscle (P = 0.06) and CSA of the tibialis anterior and gastrocnemius muscles (P < 0.0001). In the tibialis anterior muscle of aged mice, handelin upregulated mRNA levels of Igf1 (P < 0.01), anti-inflammatory cytokine Il10 (P < 0.01), mitochondrial biogenesis genes (P < 0.05) and antioxidant-related enzymes (P < 0.05) and strengthened Sod and Cat enzyme activity (P < 0.05). Handelin also reduced lipid peroxidation and protein carbonylation, downregulated mRNA levels of Fbxo32, Mstn, Cxcl1, Il1b and Tnf (P < 0.05), and decreased IL-1β levels in serum (P < 0.05). Knockdown of Hsp70 or using an Hsp70 inhibitor abolished the ameliorating effects of handelin on myotube atrophy.

CONCLUSIONS

Handelin ameliorated cachexia- and aging-induced skeletal muscle atrophy in vitro and in vivo, by maintaining homeostasis of protein synthesis and degradation, possibly by inhibiting inflammation. Handelin is a potentially promising drug candidate for the treatment of muscle wasting.

Muscle ultrasound to diagnose sarcopenia in chronic kidney disease: a systematic review and bayesian bivariate meta-analysis

OBJECTIVE

The aim of this systematic review was to assess the diagnostic test accuracy of muscle ultrasound for sarcopenia among chronic kidney disease (CKD) populations.

BACKGROUND

Sarcopenia has become a worldwide health issue, especially for CKD patients. Conventional techniques of muscle mass assessment often prove limited, thus prompts increasing interest in ultrasound suitability.

METHODS

We searched the Cochrane Library, PubMed and Embase for literature published up to June 2023. Ultrasound diagnosis of sarcopenia in CKD patients was included. Two independent investigators used the Quality Assessment Tool for Diagnosis Accuracy Studies (QUADAS-2) to assess the quality. We extracted valuable information from eligible studies. Using a Bayesian bivariate model, we pooled sensitivity and specificity values and summary receiver operating characteristic (SROC) curves.

RESULTS

Five articles, involving 428 participants at various stages of CKD were included. Three studies diagnosed by the cross-sectional area (CSA) of the rectus femoris, while two others by muscle thickness (MT) and shear wave elastography (SWE) from the same muscle, separately. Overall, CSA or SWE had a pooled sensitivity of 0.95 (95% CrI, 0.80, 1.00), and the specificity was 0.73 (95% CrI, 0.55, 0.88) for diagnosing sarcopenia in CKD patients.

CONCLUSIONS

Ultrasound measurements of CSA and SWE were more sensitive for diagnosing sarcopenia in the CKD population than in the general population. Ultrasound assessment from a single peripheral skeletal muscle site may serve as a rapid screening tool for identifying sarcopenic individuals within the CKD population, if a specific cut-off value could be determined.

Differential responses to aging amongst the transcriptome and proteome of mesenchymal progenitor populations

The biological aging of mesenchymal stem cells is proposed to contribute to the development of a range of musculoskeletal and systemic diseases associated with older adults, such as osteoporosis, sarcopenia, and frailty. Despite this, little is understood about the specific mechanisms which drive this stem cell exhaustion, with most studies evaluating indirect effects of other aging changes, such as DNA damage, senescence, and inflammaging. In this study, we assess the transcriptomic and proteomic changes in three different populations of mesenchymal progenitor cells from older (50-70 years) and younger (20-40 years) individuals to uncover potential mechanisms driving stem cell exhaustion in mesenchymal tissues. To do this, we harvested primary bone marrow mesenchymal stem and progenitor cells (MPCs), circulating osteoprogenitors (COP), and adipose-derived stem cells (ADSCs) from younger and older donors, with an equal number of samples from males and females. These samples underwent RNA sequencing and label-free proteomic analysis, comparing the younger samples to the older ones. There was a distinct transcriptomic phenotype associated with the pooled older stem cells, indicative of suppressed proliferation and differentiation; however, there was no consistent change in the proteome of the cells. Older MPCs had a distinct phenotype in both the transcriptome and proteome, again consistent with altered differentiation and proliferation, but also a pro-inflammatory immune shift in older adults. COP cells showed a strong transcriptomic shift to pro-inflammatory signaling but no consistent proteomic phenotype. Similarly, ADSCs displayed transcriptomic shift in physiologies associated with cell migration, adherence, and immune activation, but no consistent proteomic change with age. These results show that there are underlying transcriptomic changes with stem cell aging that likely contribute to a decline in tissue regeneration; however, contextual factors such as the microenvironment and general health status also have a strong role in this.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Frailty and sarcopenia: A bibliometric analysis of their association and potential targets for intervention

Frailty and sarcopenia are age-related diseases, and exhibit a concomitant relationship, as they share many common clinical features and etiological factors. Transitions within frailty status would be influenced by the presence of sarcopenia. Investigating their association to devise efficacious intervention and management strategies for geriatric patients is imperative, given their potentially unfavorable outcomes. In this study, the literature on sarcopenia and frailty was screened in the Web of Science core collection database over the past 30 years to ascertain the link between them through bibliometric analysis and the exploration of disease-related molecular pathways within the GeneCards and OMIM databases was conducted. Per inclusion and exclusion criteria, 3889 literature sources were selected for subsequent analysis. Keywords, including "cirrhosis" and "postoperative complications," represent the current and potential future research trends and focal points in this field. Moreover, 63 common potential targets between the two diseases were identified. Their pathogenesis involved cellular aging and endocrine metabolism regulation pathways, including AMPK, cell senescence, and the endocrine resistance pathway. This study identified an intimate correlation between frailty and sarcopenia in pathogenesis, prevention, and treatment measures, establishing a foundation for exploring shared prevention and treatment strategies for these two disorders.

Circulating exosome-like vesicle and skeletal muscle microRNAs are altered with age and resistance training

The age-related loss of skeletal muscle mass and functionality, known as sarcopenia, is a critical risk factor for morbidity and all-cause mortality. Resistance exercise training (RET) is the primary countermeasure to fight sarcopenia and ageing. Altered intercellular communication is a hallmark of ageing, which is not well elucidated. Circulating extracellular vesicles (EVs), including exosomes, contribute to intercellular communication by delivering microRNAs (miRNAs), which modulate post-translational modifications, and have been shown to be released following exercise. There is little evidence regarding how EVs or EV-miRNAs are altered with age or RET. Therefore, we sought to characterize circulating EVs in young and older individuals, prior to and following a 12-week resistance exercise programme. Plasma EVs were isolated using size exclusion chromatography and ultracentrifugation. We found that ageing reduced circulating expression markers of CD9, and CD81. Using late-passage human myotubes as a model for ageing in vitro, we show significantly lower secreted exosome-like vesicles (ELVs). Further, levels of circulating ELV-miRNAs associated with muscle health were lower in older individuals at baseline but increased following RET to levels comparable to young. Muscle biopsies show similar age-related reductions in miRNA expressions, with largely no effect of training. This is reflected in vitro, where aged myotubes show significantly reduced expression of endogenous and secreted muscle-specific miRNAs (myomiRs). Lastly, proteins associated with ELV and miRNA biogenesis were significantly higher in both older skeletal muscle tissues and aged human myotubes. Together we show that ageing significantly affects ELV and miRNA cargo biogenesis, and release. RET can partially normalize this altered intercellular communication. KEY POINTS: We show that ageing reduces circulating expression of exosome-like vesicle (ELV) markers, CD9 and CD81. Using late-passage human skeletal myotubes as a model of ageing, we show that secreted ELV markers are significantly reduced in vitro. We find circulating ELV miRNAs associated with skeletal muscle health are lower in older individuals but can increase following resistance exercise training (RET). In skeletal muscle, we find altered expression of miRNAs in older individuals, with no effect of RET. Late-passage myotubes also appear to have aberrant production of endogenous myomiRs with lower abundance than youthful counterparts In older skeletal muscle and late-passage myotubes, proteins involved with ELV- and miRNA biogenesis are upregulated.

Mitochondria Transplantation from Stem Cells for Mitigating Sarcopenia

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

"We want more": perspectives of sarcopenic older women on the feasibility of high-intensity progressive resistance exercises and a whey-protein nutrition intervention

This qualitative study is nested within a 12-week pilot randomized-controlled, two-arm trial involving high-intensity progressive resistance training (PRT) or PRT with a multi-nutrient, whey-protein supplementation (PRT+WP) in sarcopenic older adults (trial registration no: TCTR20230703001). The aim was to investigate sarcopenic participants' perceptions and barriers to this multi-modal intervention strategy that may accelerate "real-world" implementation. Eighteen older adults (one man) with possible sarcopenia were invited to join the study, of whom 16 women were randomized to a thrice-weekly PRT (n = 8) program (80% of 1-repetitive maximum, six resistance band exercises) only or PRT plus daily weekday milk-based WP supplementation (PRT+WP, n = 8). Muscle strength (handgrip and 5-times sit-to-stand), mass (dual-energy X-ray absorptiometry), performance (Short Physical Performance Battery and stair ascent-descent), and nutrition status (Mini Nutritional Assessment) were assessed for changes. We randomly selected eight women for the semi-structured interview. Post-intervention, eight (50%) women were sarcopenia-free, six (38%) remained in possible sarcopenia, one (6%) improved to sarcopenia, and one (6%) deteriorated from possible to severe sarcopenia. There were no significant between-group differences, but significant within-group improvements (p < 0.05) were detected for handgrip strength (PRT+WP 5.0 kg, d = 0.93; PRT 6.1 kg, d = 0.55), 5-times sit-to-stand time (PRT 2.0 s, d = 1.04), nutrition score (PRT+WP 3.44, d = 0.52; PRT 1.80, d = 0.44), and stair ascent time (PRT+WP 0.97 s, d = 0.77; PRT 0.75 s, d = 0.97). Our thematic analyses identified four main themes, namely, (1) perceived benefits, (2) sustaining behavior changes, (3) challenges in participating, and (4) improved wellbeing. Participants expressed how they initially were skeptical and doubted that they could complete the exercises or tolerate the milk-based WP supplements. However, they reported positive experiences and benefits felt from strength gains, increased confidence, and better physical abilities. Participants were surprised by the zero adverse effects of WP supplements. The women wanted more nutritional information and structured, guided exercise programs and suggested a community-based implementation. In conclusion, our findings showed PRT was well received and may support reduced risks of sarcopenia. No added benefits were seen with the addition of WP supplementation, but a larger sample is required to address this question. Overall, older (previously sarcopenic) Malay women indicated that they want more multi-modal programs embedded in their community.

Fatiguing freestyle swimming modifies miRNA profiles of circulating extracellular vesicles in athletes

Extracellular vesicles (EVs) are secreted by various tissues and cells under normal physiological or pathological conditions. Exercise-induced EVs may be involved in the adaptation of exercise-induced fatigue. The 1500-m freestyle is the longest pool-based swimming event in the Olympic Games, and there is a paucity of information regarding changes in the miRNA profiles of circulating EVs after a single session of fatiguing swimming. In this study, 13 male freestyle swimmers conducted a fatiguing 1500-m freestyle swimming session at the speed of their best previously recorded swimming performance. Fasting venous blood was collected before and after the swimming session for analysis. 70 miRNAs from the circulating EVs were found to be differentially expressed after the fatiguing 1500-m freestyle swimming session, among which 45 and 25 miRNAs were up-regulated and down-regulated, respectively. As for the target genes of five miRNAs (miR-144-3p, miR-145-3p, miR-509-5p, miR-891b, and miR-890) with the largest expression-fold variation, their functional enrichment analysis demonstrated that the target genes were involved in the regulation of long-term potentiation (LTP), vascular endothelial growth factor (VEGF), glutathione metabolism pathway, dopaminergic synapse, signal transmission, and other biological processes. In summary, these findings reveal that a single session of fatiguing swimming modifies the miRNAs profiles of the circulating EVs, especially miR-144-3p, miR-145-3p, miR-509-5p, miR-891b, and miR-890, which clarifies new mechanisms for the adaptation to a single session of fatiguing exercise from the perspective of EV-miRNAs.

Mitochondrial dysfunction: roles in skeletal muscle atrophy

Mitochondria play important roles in maintaining cellular homeostasis and skeletal muscle health, and damage to mitochondria can lead to a series of pathophysiological changes. Mitochondrial dysfunction can lead to skeletal muscle atrophy, and its molecular mechanism leading to skeletal muscle atrophy is complex. Understanding the pathogenesis of mitochondrial dysfunction is useful for the prevention and treatment of skeletal muscle atrophy, and finding drugs and methods to target and modulate mitochondrial function are urgent tasks in the prevention and treatment of skeletal muscle atrophy. In this review, we first discussed the roles of normal mitochondria in skeletal muscle. Importantly, we described the effect of mitochondrial dysfunction on skeletal muscle atrophy and the molecular mechanisms involved. Furthermore, the regulatory roles of different signaling pathways (AMPK-SIRT1-PGC-1α, IGF-1-PI3K-Akt-mTOR, FoxOs, JAK-STAT3, TGF-β-Smad2/3 and NF-κB pathways, etc.) and the roles of mitochondrial factors were investigated in mitochondrial dysfunction. Next, we analyzed the manifestations of mitochondrial dysfunction in muscle atrophy caused by different diseases. Finally, we summarized the preventive and therapeutic effects of targeted regulation of mitochondrial function on skeletal muscle atrophy, including drug therapy, exercise and diet, gene therapy, stem cell therapy and physical therapy. This review is of great significance for the holistic understanding of the important role of mitochondria in skeletal muscle, which is helpful for researchers to further understanding the molecular regulatory mechanism of skeletal muscle atrophy, and has an important inspiring role for the development of therapeutic strategies for muscle atrophy targeting mitochondria in the future.

Influence of 12-Week Concurrent Training on Exosome Cargo and Its Relationship with Cardiometabolic Health Parameters in Men with Obesity

Exosome release varies depending on the physiological state of the cell, so they could play a fundamental role in obesity, the biggest pandemic in today's societies. The beneficial effects that physical activity has both on weight and cardiovascular parameters may be mediated by exosomes released in response to exercise. Thus, we aimed (I) to study the influence of a 12-week CT intervention on exosome cargo modifications in men with obesity and (II) to determine whether changes in exosomes after the intervention were related to changes in cardiometabolic health parameters in our cohorts. An experimental, controlled design was performed in twelve (nine with valid data) adult male obese patients (mean values: 41.6 years old, 97.6 kg and 32.4 kg/m²) who were randomly divided into a control group (n = 4) and a training group (n = 5), which completed 36 sessions of CT (concurrent training) for 12 weeks. Before and after the training period, cardiometabolic health parameters were evaluated and blood samples to measure exosomes and proteins were drawn. No changes were observed in the levels of any exosomal markers and proteins; however, associations of changes between CD81 and both fat mass and weight, Flot-1 and VO_2max, HSP70 and both CRP and left ventricle diastolic diameter or CD14 and leptin were found (all p ≤ 0.05). Although the current CT was not able to clearly modify the exosome cargo, a certain medium to large clinical effect was manifested considering the nature of this study. Moreover, the associations found between the promoted changes in cardiometabolic parameters and exosome-carried proteins could indicate a relationship to be considered for future treatments in patients with obesity.

Muscle-derived exosomes and exercise in cancer prevention

There are a lot of evidences on the beneficial effects mediated by exercise on the prevention of not communicable diseases (NCDs) including different type of cancer. The production of circulating exerkines transported in exosomes represents a novel pathway activated by exercise. However, the biological mechanisms that could explain the role of exosomes in cancer prevention have been not fully elucidated. The aim of this mini-review is to provide an update on the biological mechanisms bringing the release of muscle-derived exosomes during exercise and cancer prevention.

Myoblast-derived exosomal Prrx2 attenuates osteoporosis via transcriptional regulation of lncRNA-MIR22HG to activate Hippo pathway

BACKGROUND

Sarcopenia and osteoporosis are common diseases that predominantly affect older individuals. The interaction between muscle and skeleton exerts pivotal roles in bone remodeling. This study aimed to explore the function of myoblast-derived exosomal Prrx2 in osteogenic differentiation and its potential mechanisms.

METHODS

Exosomes were isolated from myogenic differentiated C2C12 cells. qRT-PCR and Western blotting were used to determine target molecule expression. Osteogenic differentiation of BMSCs was evaluated by Alizarin red staining, ALP activity and levels of OCN, OPN, RUNX2, and BMP2. Dual-luciferase reporter assay, RIP, and ChIP assays were performed to verify the interaction between molecules. The nuclear translocation of YAP1 was observed by immunofluorescence staining. In vivo osteoporotic model was established by ovariectomy in mice. Bone loss was examined using HE staining.

RESULTS

Prrx2 expression was elevated in myogenic differentiated C2C12 cells and their exosomes. Myoblast-derived exosomal Prrx2 enhanced osteogenic differentiation of BMSCs. Delivering exosomal Prrx2 directly bond to MIR22HG promoter and promoted its transcription and expression. MIR22HG enhanced expression and nuclear translocation of YAP via sponging miR-128, thus facilitating BMSC osteogenic differentiation. Knockdown of exosomal Prrx2 suppressed osteogenic differentiation, which could be abolished by MIR22HG overexpression. Similarly, miR-128 inhibitor or YAP overexpression reversed the inhibitory effect of MIR22HG depletion or miR-128 mimics on osteogenic differentiation. Finally, myoblast-derived exosomal Prrx2 alleviated osteoporosis in mice via up-regulating MIR22HG and activating the Hippo pathway.

CONCLUSION

Myoblast-derived exosomal Prrx2 contributes to transcriptional activation of MIR22HG to activate YAP pathway via sponging miR-128, thereby facilitating osteogenic differentiation of BMSCs.

Sarcopenia: prevalence and its main risk factors in older women

Introduction: Sarcopenia is a major public health concern. It is defined as a progressive and gen­eralized skeletal muscle disorder that is associated with an increased likelihood of falls, fractures, physical disability, and ultimately, premature death.   Objective: The aim of the study was to assess the prevalence and determine the role of physical activity, nutrient intake, and selected risk factors for the development of sarcopenia in older women.   Methods: The study involved 302 women aged ≥65 years (mean age: 72.1± 5.9 years). Bioelectrical impedance analysis of body composition, static muscle strength measurements, Timed Up and Go test, and the assessment of current physical activity using accelerometers were performed. Diets were assessed using the 24-h recall method from two non-consecutive days. The energy and nutrient content of diets was calculated using the computer program DIETA 6.   Results: Sarcopenia was present in 28.8% of the women studied. The most important factor in the decrease in the risk of sarcopenia was protein intake ≥ 0.9 g/kg b.m. (OR=0.08;p<0.001), and physical activity ≥ 4000 steps/day. However, these results were not statistically significant (OR=0.58; p=0.08). Furthermore, the risk of developing sarcopenia increased as BMI (OR=1.36; p<0.001) or percent of body fat (OR=1.29; p<0.001) increased.

Identification of a novel small-molecule inhibitor of miR-29b attenuates muscle atrophy

Muscle atrophy is debilitating and can be induced by several stressors. Unfortunately, there are no effective pharmacological treatment until now. MicroRNA (miR)-29b is an important target that we identified to be commonly involved in multiple types of muscle atrophy. Although sequence-specific inhibition of miR-29b has been developed, in this study, we report a novel small-molecule miR-29b inhibitor that targets miR-29b hairpin precursor (pre-miR-29b) (Targapremir-29b-066 [TGP-29b-066]) considering both its three-dimensional structure and the thermodynamics of interaction between pre-miR-29b and the small molecule. This novel small-molecule inhibitor has been demonstrated to attenuate muscle atrophy induced by angiotensin II (Ang II), dexamethasone (Dex), and tumor necrosis factor α (TNF-α) in C2C12 myotubes, as evidenced by increase in the diameter of myotube and decrease in the expression of Atrogin-1 and MuRF-1. Moreover, it can also attenuate Ang II-induced muscle atrophy in mice, as evidenced by a similar increase in the diameter of myotube, reduced Atrogin-1 and MuRF-1 expression, AKT-FOXO3A-mTOR signaling activation, and decreased apoptosis and autophagy. In summary, we experimentally identified and demonstrated a novel small-molecule inhibitor of miR-29b that could act as a potential therapeutic agent for muscle atrophy.

The effect of combining nutrient intake and physical activity levels on central obesity, sarcopenia, and sarcopenic obesity: a population-based cross-sectional study in South Korea

BACKGROUND

This study was conducted to investigate the effects of combining nutritional and physical activity (PA) factors on four different categories, according to the presence or absence of sarcopenia and central obesity.

METHODS

From the 2008-2011 Korea National Health and Nutrition Examination Survey, 2971 older adults aged ≥ 65 years were included and divided into four groups based on their sarcopenia and central obesity status: healthy control (39.3%), central obesity (28.9%), sarcopenia (27.4%), and sarcopenic obesity (4.4%). Central obesity was defined as a waist circumference of ≥ 90 cm in men and ≥ 85 cm in women. Sarcopenia was defined as an appendicular skeletal mass index of < 7.0 kg/m2 in men and < 5.4 kg/m2 in women, and sarcopenic obesity was defined as the coexistence of sarcopenia and central obesity.

RESULTS

Participants who consumed more energy and protein than the average requirement had a lower likelihood of having sarcopenia (odds ratio (OR): 0.601, 95% confidence interval (CI): 0.444-0.814) than those who did not consume enough nutrients. The likelihood of central obesity and sarcopenic obesity decreased in groups with recommended PA levels, regardless of whether energy intake met or did not meet the average requirement. Whether PA met or did not meet the recommended level, the likelihood of sarcopenia decreased in groups with energy intake that met the average requirement. However, when PA and energy requirements were met, there was a greater reduction in the likelihood of sarcopenia (OR: 0.436, 95% CI: 0.290-0.655).

CONCLUSION

These findings suggest that adequate energy intake that meets requirements is more likely to be effective as a major prevention and treatment goal for sarcopenia, whereas PA guidelines should be prioritized in the case of sarcopenic obesity.

Prefrailty subtypes differentially predict 5-year mortality in the functionally independent geriatric population

INTRODUCTION

Both frailty and prefrailty (PF) are related to mortality. However, there is no consensus about the PF subtypes for prediction of the mortality risk. We aimed to compare the 5-year mortality of functionally independent geriatric outpatients with nonfrailty, different PF subtypes and frailty.

METHODS

This was a single-center, retrospective cohort study. Community-dwelling older adults who visited the geriatric outpatient clinic in a healthcare institution in Taiwan were enrolled. PF1 was defined based on exhaustion and/or body weight loss whereas PF2 was defined by one or two of the following criteria: weakness, slowness, and low physical activity. Frailty was defined by three or more above criteria. Demographics and results of comprehensive geriatric assessment were compared and Kaplan-Meier survival analysis was used to determine the 5-year survival among the nonfrail, PF1, PF2 and frail groups.

RESULTS

Of the 982 participants, the proportion of PF and frailty was high (PF 45.7% and frailty 24.5%). The cumulative 5-year survival rate of the nonfrail group, PF1, PF2 subgroups and frail group was 98.6%, 95.8%, 89.1% and 81.3% respectively. Age, male sex, PF2 subtype and frailty were significantly associated with 5-year mortality [hazard ratio (95% confidence interval) 1.05 (1.01-1.08), 1.96 (1.08-3.57), 5.18 (1.57-17.09), and 6.87 (2.05-23.04), respectively].

DISCUSSION AND CONCLUSION

The proportion of PF and frailty was high in old outpatient population with functional independence. PF2 subtypes and frailty could influence the 5-year mortality risk in these participants. Identifying PF2 participants earlier and instituting prompt intervention may be beneficial in older patients.

The syndromic triad of COVID-19, type 2 diabetes, and malnutrition

The coronavirus disease 2019 (COVID-19) pandemic challenges our collective understanding of transmission, prevention, complications, and clinical management of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Risk factors for severe infection, morbidity, and mortality are associated with age, environment, socioeconomic status, comorbidities, and interventional timing. Clinical investigations report an intriguing association of COVID-19 with diabetes mellitus and malnutrition but incompletely describe the triphasic relationship, its mechanistic pathways, and potential therapeutic approaches to address each malady and their underlying metabolic disorders. This narrative review highlights common chronic disease states that interact epidemiologically and mechanistically with the COVID-19 to create a syndromic phenotype-the COVID-Related Cardiometabolic Syndrome-linking cardiometabolic-based chronic disease drivers with pre-, acute, and chronic/post-COVID-19 disease stages. Since the association of nutritional disorders with COVID-19 and cardiometabolic risk factors is well established, a syndromic triad of COVID-19, type 2 diabetes, and malnutrition is hypothesized that can direct, inform, and optimize care. In this review, each of the three edges of this network is uniquely summarized, nutritional therapies discussed, and a structure for early preventive care proposed. Concerted efforts to identify malnutrition in patients with COVID-19 and elevated metabolic risks are needed and can be followed by improved dietary management while simultaneously addressing dysglycemia-based chronic disease and malnutrition-based chronic disease.

Extracellular Vesicles from NMN Preconditioned Mesenchymal Stem Cells Ameliorated Myocardial Infarction via miR-210-3p Promoted Angiogenesis

Mesenchymal stem cell-derived extracellular vesicles (MSCs-EVs) possess cardioprotection in acute myocardial infarction. Nevertheless, the therapeutic intervention potential and the molecular mechanism of EVs from NMN (Nicotinamide mononucleotide) preconditioned hUCMSCs (N-EVs) in acute myocardial infarction remains unknown. In the present study, EVs from hUCMSCs (M-EVs) and N-EVs were identified by electron microscopy, immunoblotting and nanoparticle tracking analysis. Compared with M-EVs, N-EVs significantly increased the proliferation, migration, and angiogenesis of HUVECs. Meanwhile, N-EVs markedly reduced apoptosis and cardiac fibrosis and promoted angiogenesis in the peri-infarct region in the MI rats. A high-throughput miRNA sequencing and qPCR methods analysis revealed that miR-210-3p was abundant in N-EVs and the expression of miR-210-3p was obviously upregulated in HUVECs after N-EVs treated. Overexpression of miR-210-3p in HUVECs significantly enhanced the tube formation, migration and proliferative capacities of HUVECs. However, downregulation of miR-210-3p in HUVECs markedly decreased the tube formation, migration and proliferative capacities of HUVECs. Furthermore, bioinformatics analysis and luciferase assays revealed that EphrinA3 (EFNA3) was a direct target of miR-210-3p. Knockdown of miR-210-3p in N-EVs significantly impaired its ability to protect the heart after myocardial infarction. Altogether, these results indicated that N-EVs promoted the infarct healing through improvement of angiogenesis by miR-210-3p via targeting the EFNA3. Created with Biorender.com.

Potential Value and Application of Liquid Biopsy in Tumor, Neurodegeneration, and Muscle Degenerative Diseases

Liquid biopsy provides a promising alternative for the detection of disease-specific markers due to its superior noninvasive and original tissue representativeness. Liquid biopsies have a wide range of health and disease applications involving components ranging from circulating cells to acellular nucleic acid molecules and other metabolites. Here, we review the different components of liquid biopsy and investigate the most advanced noninvasive methods for detecting these components as well as their existing problems and trends. In particular, we emphasize the importance of analyzing liquid biopsy data from extracellular vesicles and small nucleic acids in neurological and muscle degeneration, with the aim of using this technique to enhance personalized healthcare. Although previous reviews have focused on cancer, this review mainly emphasizes the potential application of extracellular vesicles and microRNAs in liquid biopsy in neurodegeneration and muscle degeneration.

Complementary combination of biomarkers for diagnosis of sarcopenia in C57BL/6J mice

AIMS

The objective of this study is to provide a reliable strategy for the diagnosis of sarcopenia based on a complementary combination of biomarkers from various approaches.

MATERIAL AND METHODS

A total of 30 C57BL/6J mice were used for the experiment, in which 15 young mice (YM) at 24 weeks old and 15 aged mice (AM) at 88 weeks old. Extracted features-based digital biomarkers from the electromyography activity of tibialis anterior muscles were evaluated by using receiver operating characteristic analysis. Extracted tissular proteins and circulating hormones based chemical biomarkers were investigated by using immunoblotting and enzyme-linked immunosorbent assay.

KEY FINDINGS

In terms of digital biomarkers, the feature-based classification of mice groups showed good performance (Feature A: AUC = 0.986, accuracy = 0.928) and (Feature B: AUC = 0.999, accuracy = 0.990). On the other hand, muscle-specific protein levels based chemical biomarkers (e.g. MuRF1, FoxO1, and perilipin2) were observed significantly increase with age. Pro-inflammatory cytokines based biomarkers extracted from muscle tissue and circulating plasma (e.g. TNF-α, IL-6, and IL-8) were significantly higher in case of AM group compared to YM group. Circulating hormone-based chemical biomarkers (e.g. cortisol/DHEA ratio and cathepsin D) presented a significant increase in concentrations with age. Circulating neurotransmitter based biomarkers (e.g. acetylcholine, serotonin, and histamine) also increased significantly in concentrations from YM to AM.

SIGNIFICANCE

A complementary combination of digital and chemical biomarkers covers multiple domains of sarcopenia to provide an effective strategy for the early diagnosis of sarcopenia.

Lipotoxicity-related sarcopenia: a review

A body of literature supports the postulation that a persistent lipid metabolic imbalance causes lipotoxicity, "an abnormal fat storage in the peripheral organs". Hence, lipotoxicity could somewhat explain the process of sarcopenia, an aging-related, gradual, and involuntary decline in skeletal muscle strength and mass associated with several health complications. This review focuses on the recent mechanisms underlying lipotoxicity-related sarcopenia. A vicious cycle occurs between sarcopenia and ectopic fat storage via a complex interplay of mitochondrial dysfunction, pro-inflammatory cytokine production, oxidative stress, collagen deposition, extracellular matrix remodeling, and life habits. The repercussions of lipotoxicity exacerbation of sarcopenia can include increased disability, morbidity, and mortality. This suggests that appropriate lipotoxicity management should be considered the primary target for the prevention and/or treatment of chronic musculoskeletal and other aging-related disorders. Further advanced research is needed to understand the molecular details of lipotoxicity and its consequences for sarcopenia and sarcopenia-related comorbidities.

Decrotonylation of AKT1 promotes AKT1 phosphorylation and activation during myogenic differentiation

INTRODUCTION

Myogenic differentiation plays an important role in pathophysiological processes including muscle injury and regeneration, as well as muscle atrophy. A novel type of posttranslational modification, crotonylation, has been reported to play a role in stem cell differentiation and disease. However, the role of crotonylation in myogenic differentiation has not been clarified.

OBJECTIVES

This study aims to find the role of crotonylation during myogenic differentiation and explore whether it is a potential target in myogenic dysfunction disease.

METHODS

C2C12 cell line and skeletal muscle mesenchymal progenitors of Mus musculus were used for myogenic process study in vitro, while muscle injury model of mice was used for in vivo muscle regeneration study. Mass spectrometry favored in discovery of potential target protein of crotonylation and its specific sites.

RESULTS

We confirmed the gradual decrease in total protein crotonylation level during muscle differentiation and found decreased crotonylation of AKT1, which facilitated an increase in AKT1 phosphorylation. Then we verified that crotonylation of AKT1 at specific sites weakened its binding with PDK1 and impaired its phosphorylation. In addition, we found that increased expression of the crotonylation eraser HDAC3 decreased AKT1 crotonylation levels during myogenic differentiation, jointly promoting myogenic differentiation.

CONCLUSION

Our study highlights the important role of decrotonylation of AKT1 in the process of muscle differentiation, where it aids the phosphorylation and activation of AKT1 and promotes myogenic differentiation. This is of great significance for exploring the pathophysiological process of muscle injury repair and sarcopenia.

Ultrasonography for Assessment of Sarcopenia: A Primer

The human skeletal muscle has a pivotal role in preserving health by maintaining mobility, balance, and metabolic homeostasis. Significant muscle loss as a part of aging and accelerated by disease leads to sarcopenia which becomes an important predictor of quality of life in older persons. Therefore, clinical screening for sarcopenia and validation by precise qualitative and quantitative measurement of skeletal muscle mass (MM) and function is at the center-stage of translational research. Many imaging modalities are available, each having their strengths and limitations, either in interpretation, technical processes, time constraints, or expense. B-mode ultrasonography (US) is a relatively novel approach to evaluating muscle. It can measure several parameters such as MM and architecture simultaneously including muscle thickness, cross-sectional area, echogenicity, pennate angle, and fascicle length. It can also evaluate dynamic parameters like muscle contraction force and muscle microcirculation. US has not gained global attention due to a lack of consensus on standardization and diagnostic threshold values to diagnose sarcopenia. However, it is an inexpensive and widely available technique with clinical applicability. The ultrasound-derived parameters correlate well with strength and functional capacity and provide potential prognostic information. Our aim is to present an update on the evidence-based role of this promising technique in sarcopenia, its advantages over the existing modalities, and its limitations in actual practice with the hope that it may emerge as the "stethoscope" for community diagnosis of sarcopenia.

Differential effects of calorie restriction and rapamycin on age-related molecular and functional changes in skeletal muscle

Aging is a multifactorial process associated with progressive degradation of physiological integrity and function. One of the greatest factors contributing to the deleterious effects of aging is the decline of functional ability due to loss of muscle mass, strength, and function, a condition termed sarcopenia. Calorie restriction (CR) has consistently been shown to extend lifespan and delay the onset and progression of various age-related diseases, including sarcopenia. Additional anti-aging interventions that are receiving scientific attention are CR mimetics. Of these pharmacological compounds, rapamycin has shown similar CR-related longevity benefits without the need for diet restrictions. To investigate the potential role of rapamycin as an anti-sarcopenic alternative to CR, we conducted a study in male and female C57BL/6 J mice to assess the effects of rapamycin on age-related gene expression changes in skeletal muscle associated with loss of muscle mass, strength, and function, relative to control. We hypothesize that the effects of rapamycin will closely align with CR with respect to physical function and molecular indices associated with muscle quality. Our results indicate CR and rapamycin provide partial protection against age-related decline in muscle, while engaging uniquely different molecular pathways in skeletal muscle. Our preclinical findings of the therapeutic potential of rapamycin or a CR regimen on geroprotective benefits in muscle should be extended to translational studies towards the development of effective strategies for the prevention and management of sarcopenia.

Tanshinone IIA protects against chronic obstructive pulmonary disease via exosome‑shuttled miR‑486‑5p

Chronic obstructive pulmonary disease (COPD) is one of the major causes of death worldwide today, and its related morbidity has been predicted to show an increase in subsequent years. Recent studies have shown that Danshen, a Chinese herbal medicine, is a potential drug in the treatment of inflammation-related lung diseases. COPD was induced in this study using cigarette smoke (CS) exposure plus intranasal inhalation of lipopolysaccharide to ascertain whether the main pharmacological component from Danshen, tanshinone IIA (TIIA), and its water soluble form, sodium tanshinone IIA sulfonate (STS), protect against the development of COPD. The weight, lung function, hematoxylin and eosin staining, and Masson Trichrome determinations revealed that TIIA inhalation attenuated lung dysfunction in COPD mice induced by cigarette smoke and lipopolysaccharide exposure. In addition, exosomes derived from TIIA-treated COPD mice exerted similar protective effects against COPD, suggesting that TIIA may protect against COPD through exosome-shuttled signals. miR-486-5p was found to be a key molecule in mediating the protective effects of exosomes derived from TIIA-treated COPD mice using miRNA sequencing and cellular screening. Treatment of COPD mice with an agomiR of miR-486-5p protected lung function in COPD mice, and treatment of COPD mice with an antagomir of miR-486-5p abolished the protective effects of TIIA. Moreover, luciferase activity reporter assay, RT-qPCR, and western blot analyses showed that miR-486-5p exerted protective effects against COPD via targeting phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1). These results suggest that STS protects against COPD through upregulation of miR-486-5p, and that TIIA or miR-486-5p is a potential drug for the treatment of COPD.

A pas de deux of osteoporosis and sarcopenia: osteosarcopenia

The musculoskeletal conditions osteoporosis and sarcopenia are highly prevalent in older adults. Osteoporosis is characterized by low bone mass and microarchitectural deterioration of bone, whereas sarcopenia is identified by the loss of muscle strength, function and mass. Osteoporosis represents a major health problem contributing to millions of fractures worldwide on an annual basis, whereas sarcopenia is associated with a range of adverse physical and metabolic outcomes. They both affect physical and social function, confidence and quality of life as well as contributing to high health-care costs worldwide. Osteosarcopenia is the term given when both conditions occur concomitantly and it has been suggested that interactions between these two conditions may accelerate individual disease progression as co-existence of osteoporosis and sarcopenia is associated with higher morbidity from falls, fracture, disability as well as mortality. In this review, we will outline the epidemiology, pathogenesis and clinical consequences of osteosarcopenia and discuss available management strategies.

Cellular Senescence in Sarcopenia: Possible Mechanisms and Therapeutic Potential

Aging promotes most degenerative pathologies in mammals, which are characterized by progressive decline of function at molecular, cellular, tissue, and organismal levels and account for a host of health care expenditures in both developing and developed nations. Sarcopenia is a prominent age-related disorder in musculoskeletal system. Defined as gradual and generalized chronic skeletal muscle disorder, sarcopenia involves accelerated loss of muscle mass, strength and function, which is associated with increased adverse functional outcomes and evolutionally refers to muscle wasting accompanied by other geriatric syndromes. More efforts have been made to clarify mechanisms underlying sarcopenia and new findings suggest that it may be feasible to delay age-related sarcopenia by modulating fundamental mechanisms such as cellular senescence. Cellular senescence refers to the essentially irreversible growth arrest mainly regulated by p53/p21^CIP1 and p16^INK4a/pRB pathways as organism ages, possibly detrimentally contributing to sarcopenia via muscle stem cells (MuSCs) dysfunction and the senescence-associated secretory phenotype (SASP) while cellular senescence may have beneficial functions in counteracting cancer progression, tissue regeneration and wound healing. By now diverse studies in mice and humans have established that targeting cellular senescence is a powerful strategy to alleviating sarcopenia. However, the mechanisms through which senescent cells contribute to sarcopenia progression need to be further researched. We review the possible mechanisms involved in muscle stem cells (MuSCs) dysfunction and the SASP resulting from cellular senescence, their associations with sarcopenia, current emerging therapeutic opportunities based on targeting cellular senescence relevant to sarcopenia, and potential paths to developing clinical interventions genetically or pharmacologically.

The fatter, the better in old age: the current understanding of a difficult relationship

PURPOSE OF REVIEW

Obesity has shown a protective effect on mortality in older adults, also known as the obesity paradox, but there are still controversies about this relationship.

RECENT FINDINGS

Recent studies have shown a J or U-shaped relationship between BMI and mortality, wherein an optimal range is described between 22 and 37 kg/m2 depending on the condition. Many mechanisms can explain this protective effect of higher BMI, fat/muscle mass storage, more aggressive treatment in obese individuals, loss of bone mineral content and selection bias. However, BMI must be used with caution due to its limitations to determine body composition and fat distribution.

SUMMARY

Although BMI is an easy tool to evaluate obesity, its protective effect may be present to certain extend, from normal range to class I obesity (BMI 30-34.9 kg/m2), but then it becomes detrimental. Skeletal muscle mass and muscle function associated with adipose tissue assessment can add valuable information in the risk stratification. Further studies should be performed prospectively, adjust BMI for cofounding variable and consider other elderly subpopulations. To promote healthy ageing, excessive fat mass should be avoided and maintenance or improvement of skeletal muscle mass and muscle function should be stimulated in older adults.

Alterations in Autophagy and Mammalian Target of Rapamycin (mTOR) Pathways Mediate Sarcopenia in Patients with Cirrhosis

Background and aims

The pathophysiology of sarcopenia in cirrhosis is poorly understood. We aimed to evaluate the histological alterations in the muscle tissue of patients with cirrhosis and sarcopenia, and identify the regulators of muscle homeostasis.

Methods

Computed tomography images at third lumbar vertebral level were used to assess skeletal muscle index (SMI) in 180 patients. Sarcopenia was diagnosed based on the SMI cut-offs from a population of similar ethnicity. Muscle biopsy was obtained from the vastus lateralis in 10 sarcopenic patients with cirrhosis, and the external oblique in five controls (voluntary kidney donors during nephrectomy). Histological changes were assessed by hematoxylin and eosin staining and immunohistochemistry for phospho-FOXO3, phospho-AKT, phospho-mTOR, and apoptosis markers (annexin V and caspase 3). The messenger ribonucleic acid (mRNA) expressions for MSTN, FoxO3, markers of ubiquitin-proteasome pathway (FBXO32, TRIM63), and markers of autophagy (Beclin-1 and LC3) were also quantified.

Results

The prevalence of sarcopenia was 14.4%. Muscle histology in sarcopenics showed atrophic angulated fibers (P = 0.002) compared to controls. Immunohistochemistry showed a significant loss of expression of phospho-mTOR (P = 0.026) and an unaltered phospho-AKT (P = 0.089) in sarcopenic patients. There were no differences in the immunostaining for annexin-V, caspase-3, and phospho-FoxO3 between the two groups. The mRNA expressions of MSTN and Beclin-1 were higher in sarcopenics (P = 0.04 and P = 0.04, respectively). The two groups did not differ in the mRNA levels for TRIM63, FBXO32, and LC3.

Conclusions

Significant muscle atrophy, increase in autophagy, MSTN gene expression, and an impaired mTOR signaling were seen in patients with sarcopenia and cirrhosis.

Pyruvate Might Bridge Gut Microbiota and Muscle Health in Aging Mice After Chronic High Dose of Leucine Supplementation

Background: The previous studies demonstrated that there might be complex and close relationships among leucine supplementation, gut microbiota, and muscle health, which still needs further investigation.

Aims: This study aimed to explore the associations of gut microbiota with muscle health after leucine intake.

Methods: In this study, 19-month-old male C57BL/6j mice (n = 12/group) were supplemented with ultrapure water, low dose of leucine (500 mg/kg·d), and high dose of leucine (1,250 mg/kg·d) for 12 weeks by oral gavage. The mice fecal samples in each group before and after supplementation were collected for baseline and endpoint gut microbiota analysis by using 16S rDNA amplicon sequencing. Meanwhile, ultrasound measurement, H&E staining, myofiber cross-sectional area (CSA) measurement, and western blotting were performed in the quadriceps subsequently. The pyruvate levels were detected in feces.

Results: Improvement in muscle of histology and ultrasonography were observed after both low and high dose of leucine supplementation. High dose of leucine supplementation could promote skeletal muscle health in aging mice via regulating AMPKα/SIRT1/PGC-1α. The richness and diversities of microbiota as well as enriched metabolic pathways were altered after leucine supplementation. Firmicutes-Bacteroidetes ratio was significantly decreased in high-leucine group. Moreover, pyruvate fermentation to propanoate I were negatively associated with differential species and the pyruvate levels were significantly increased in feces after high dose of leucine supplementation.

Conclusions: Chronic high dose of leucine supplementation changed gut microbiota composition and increased pyruvate levels in the feces, which possibly provides a novel direction for promoting muscle health in aging mice.

Value of ultrasound in grading the severity of sarcopenia in patients with hepatic cirrhosis

Background

Ultrasound is emerging as an efficient significant method for measuring muscle mass in patients with liver cirrhosis. It has been applied in numerous studies as an accurate measuring tool for the muscles of the limbs. This study was conducted to assess the severity of sarcopenia in liver cirrhosis patients, through utilizing ultrasound in measuring the cross-sectional area and consequently estimating the muscle mass of both the upper and lower limb muscles, than correlating the results with hand grip strength as representative of functional status. Also, the severity of sarcopenia was correlated with conventional prognostic scores for liver cirrhosis, like Child or MELD scores and detecting its effect on the duration of hospital stay and mortality.

Results

This study was conducted on 101 liver cirrhosis patients who were admitted to the internal medicine hospital, 30 healthy participants were added as a control group. Using the FNIH (Foundation for the national Institutes of health) cuff off of hand grip (< 26 kg in male and < 16 kg in female, Quadriceps muscle index cutoff was estimated to be(1.67 cm/m2 for male and 1.58 cm/m2 for female).

Ultrasound (mid upper arm, mid-thigh and Quadriceps muscle index) showed significant indirect correlation with (Child even in Child A and MELD) scores, as well as with the duration of hospital stay. Also, they showed a direct correlation with HGS.

Conclusion

Sarcopenia in cirrhotic patients assessed by ultrasonography of (mid upper arm, mid-thigh muscle thickness) and HGS are independent predictors of disease severity and poor outcome, which is assessed by high Child and MELD scores. Also, ultrasound and HGS are straightforward bedside techniques used for assessment of sarcopenia.

Potential Roles of miRNA-1245a Regulatory Networks in Sarcopenia

Objective

Sarcopenia is a universal problem in elderly individuals. The molecular regulatory mechanisms in sarcopenia are not well understood. In the present study, we explored a possible molecular mechanism involved in the pathogenesis of sarcopenia.

Methods

Differentially expressed genes (DEGs) were identified using the Gene Expression Omnibus (GEO) database. Signaling pathways related to these DEGs were identified by gene set enrichment analysis (GSEA). Pearson correlation was calculated for all the pairwise comparisons of gene expression values between coding genes and DEGs. Interactions between the proteins encoded by the DEGs were identified using the STRING database. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathway analyses were performed to predict the functions of the DEGs.

Results

Three differentially expressed miRNAs and 5 differentially expressed mRNAs were identified in association with DEGs. We found that miRNA-1245a expression in patients with sarcopenia was higher than that in healthy controls. The GSEA showed that many pathways, such as the JAK-STAT signaling pathway and pathways related to glioma, gap junctions, and regulation of the actin cytoskeleton, were enriched in the high-miRNA-1245a-expression group. A total of 127 miRNA-1245a-related mRNAs were identified. The GO and KEGG analyses revealed that miRNA-1245a had a strong effect on a number of fundamental biological processes, such as kinase activity, that are related to the development of sarcopenia.

Conclusion

Our analyses indicate that miRNA-1245a may be a potential key molecule in the diagnosis and treatment of sarcopenia, which provides a basis for the research of miRNA in sarcopenia.

Daily Leucine Intake Is Positively Associated with Lower Limb Skeletal Muscle Mass and Strength in the Elderly

Higher daily protein intake, with an emphasis on leucine content, is thought to mitigate age-related anabolic resistance, potentially counteracting age-related morphological and functional declines. The present study investigated potential associations between total daily leucine intake and dependent variables, including quadriceps muscle cross-sectional area (CSA) and maximum dynamic muscle strength (1-RM) in a cohort of healthy free-living older individuals of both sexes (n = 67; 34/33 men/women). Participants performed three 24 h dietary recalls and underwent a magnetic resonance imaging exam followed by 1-RM tests. Our results demonstrate moderate associations between total daily leucine and both quadriceps CSA (r = 0.42; p = 0.004) and 1-RM (r = 0.45; p = 0.001). Furthermore, our exploratory biphasic linear regression analyses, adjusted for sex, age, and protein intake relative to body weight, revealed a plateau for daily leucine intake and muscle mass and muscle strength (~7.6–8.0 g·day⁻¹) in older adults. In conclusion, we demonstrated that total daily leucine intake is associated with muscle mass and strength in healthy older individuals and this association remains after controlling for multiple factors, including overall protein intake. Furthermore, our breakpoint analysis revealed non-linearities and a potential threshold for habitual leucine intake, which may help guide future research on the effects of chronic leucine intake in age-related muscle loss.

Management of non-alcoholic fatty liver disease in patients with sarcopenia

INTRODUCTION

Sarcopenia usually occurs with aging, sedentary lifestyle, unhealthy dietary habits, and chronic disorders pathophysiologically and bi-directionally linked to obesity and nonalcoholic fatty liver disease (NAFLD). Because of the global increase in aging and obesity populations, patients with concomitant sarcopenia and NAFLD are common, accompanied by various disorders relevant to obesity and sarcopenia, with across-the-board impact on socio-economic and public health life worldwide. Therefore, developing effective and practical management of these patients has become a pressing clinical issue.

AREAS COVERED

The authors searched literature from PubMed and Ovid MEDLINE up until Feb 2020. Emerging data on the management of sarcopenia and nonalcoholic fatty liver disease were examined and discussed.

EXPERT OPINION

Although NAFLD in patients with sarcopenia has become a critical problem worldwide, we still don't know much about the management of such patients. Based on theoretical speculations, we can recommend lifestyle intervention, including diet control with adequate protein intake, exercise intervention, and weight reduction as the mainstay of management at the first stage. More studies are needed in the future to identify the most suitable treatment and solve this important problem.

Understanding of sarcopenia: from definition to therapeutic strategies

Sarcopenia refers to the gradual loss of skeletal muscle mass and function along with aging and is a social burden due to growing healthcare cost associated with a super-aging society. Therefore, researchers have established guidelines and tests to diagnose sarcopenia. Several studies have been conducted actively to reveal the cause of sarcopenia and find an economic therapy to improve the quality of life in elderly individuals. Sarcopenia is caused by multiple factors such as reduced regenerative capacity, imbalance in protein turnover, alteration of fat and fibrotic composition in muscle, increased reactive oxygen species, dysfunction of mitochondria and increased inflammation. Based on these mechanisms, nonpharmacological and pharmacological strategies have been developed to prevent and treat sarcopenia. Although several studies are currently in progress, no treatment is available yet. This review presents the definition of sarcopenia and summarizes recent understanding on the detailed mechanisms, diagnostic criteria, and strategies for prevention and treatment.

Lactobacillus plantarum HY7715 Ameliorates Sarcopenia by Improving Skeletal Muscle Mass and Function in Aged Balb/c Mice

Sarcopenia is a loss of muscle mass and function in elderly people and can lead to physical frailty and fall-related injuries. Sarcopenia is an inevitable event of the aging process that substantially impacts a person's quality of life. Recent studies to improve muscle function through the intake of various functional food materials are attracting attention. However, it is not yet known whether probiotics can improve muscle mass and muscle strength and affect physical performance. Lactobacillus plantarum HY7715 (HY7715) is a lactic acid bacteria isolated from kimchi. The present research shows that L. plantarum HY7715 increases physical performance and skeletal muscle mass in 80-week-old aged Balb/c male mice. HY7715 not only induces myoblast differentiation and mitochondrial biogenesis but also inhibits the sarcopenic process in skeletal muscle. In addition, HY7715 recovers the microbiome composition and beta-diversity shift. Therefore, HY7715 has promise as a functional probiotic supplement to improve the degeneration of muscle function that is associated with aging.