Muscle-Bone Crosstalk: Emerging Opportunities for Novel Therapeutic Approaches to Treat Musculoskeletal Pathologies

Impacts of osteosarcopenia on musculoskeletal health, risks of falls and fractures, and activities of daily living among population aged 50 and above: an age- and sex-matched cross-sectional analysis

AIMS

We conducted this study to investigate the impact of muscle loss on musculoskeletal health, fall and fracture risks, and activities of daily living (ADL) in elderly patients with osteoporosis.

MATERIALS AND METHODS

This age- and sex-matched cross-sectional study analyzed data from a medical center involving patients aged ≥ 50 from 2020 to 2022. The included participants were formed into three groups: 100 with osteoporosis only, 100 with osteosarcopenia, and 50 control individuals without osteoporosis and sarcopenia. We compared groups based on their baseline characteristics, bone and muscle health measurements, and the risks of falls and fractures using the STRATIFY scale and FRAX, respectively. Additionally, ADL was assessed using the Barthel Index. A multivariate analysis was performed to identify factors associated with declined ADL in osteosarcopenic patients.

RESULTS

The mean age was 76.17 years, and 82% were female. The osteosarcopenic group demonstrated poorer bone and muscle quality and quantity, with greater risks of major osteoporotic-related fractures, hip fractures, and falls, as well as significantly decreased ADL than other groups. When comparing sexes, females exhibited worse performance than males across groups. Slow gait speed and high STRATIFY score are independent predictors of declined ADL in osteosarcopenic patients.

CONCLUSION

Sarcopenia exacerbates osteoporotic patients, particularly women, worsening bone deterioration, increasing fall and fracture risks, and significantly impairing daily activities. Enhancing walking speed and reducing fall risk can boost independence in individuals with osteosarcopenia. Early detection, proper management, and preventive measures are essential for mitigating these adverse outcomes in high-risk individuals.

Poor bone health in Duchenne muscular dystrophy: a multifactorial problem beyond corticosteroids and loss of ambulation

Duchenne muscular dystrophy (DMD) is a progressive, fatal muscle wasting disease caused by X-linked mutations in the dystrophin gene. Alongside the characteristic muscle weakness, patients face a myriad of skeletal complications, including osteoporosis/osteopenia, high susceptibility to vertebral and long bone fractures, fat embolism post-fracture, scoliosis, and growth retardation. Those skeletal abnormalities significantly compromise quality of life and are sometimes life-threatening. These issues were traditionally attributed to loss of ambulation and chronic corticosteroid use, but recent investigations have unveiled a more intricate etiology. Factors such as vitamin D deficiency, hormonal imbalances, systemic inflammation, myokine release from dystrophic muscle, and vascular dysfunction are emerging as significant contributors as well. This expanded understanding illuminates the multifaceted pathogenesis underlying skeletal issues in DMD. Present therapeutic options are limited and lack specificity. Advancements in understanding the pathophysiology of bone complications in DMD will offer promising avenues for novel treatment modalities. In this review, we summarize the current understanding of factors contributing to bone problems in DMD and delineate contemporary and prospective multidisciplinary therapeutic approaches.

Collagen patches releasing phosphatidylserine liposomes guide M1-to-M2 macrophage polarization and accelerate simultaneous bone and muscle healing

Bilateral communication between bones and muscles is essential for healing composite bone-muscle injuries from orthopedic surgeries and trauma. However, these injuries are often characterized by exaggerated inflammation, which can disrupt bone-muscle crosstalk, thereby seriously delaying the healing of either tissue. Existing approaches are largely effective at healing single tissues. However, simultaneous healing of multiple tissues remains challenging, with little research conducted to date. Here we introduce collagen patches that overcome this overlooked issue by harnessing the plasticity of macrophage phenotypes. Phosphatidylserine liposomes (PSLs) capable of shifting the macrophage phenotype from inflammatory M1 into anti-inflammatory/prohealing M2 were coated on collagen patches via a layer-by-layer method. Original collagen patches failed to improve tissue healing under inflammatory conditions coordinated by M1 macrophages. In contrast, PSL-coated collagen patches succeeded in accelerating bone and muscle healing by inducing a microenvironment dominated by M2 macrophages. In cell experiments, differentiation of preosteoblasts and myoblasts was completely inhibited by secretions of M1 macrophages but unaffected by those of M2 macrophages. RNA-seq analysis revealed that type I interferon and interleukin-6 signaling pathways were commonly upregulated in preosteoblasts and myoblasts upon stimulation with M1 macrophage secretions, thereby compromising their differentiation. This study demonstrates the benefit of PSL-mediated M1-to-M2 macrophage polarization for simultaneous bone and muscle healing, offering a potential strategy toward simultaneous regeneration of multiple tissues. STATEMENT OF SIGNIFICANCE: Existing approaches for tissue regeneration, which primarily utilize growth factors, have been largely effective at healing single tissues. However, simultaneous healing of multiple tissues remains challenging and has been little studied. Here we demonstrate that collagen patches releasing phosphatidylserine liposomes (PSLs) promote M1-to-M2 macrophage polarization and are effective for simultaneous healing of bone and muscle. Transcriptome analysis using next-generation sequencing reveals that differentiation of preosteoblasts and myoblasts is inhibited by the secretions of M1 macrophages but promoted by those of M2 macrophages, highlighting the importance of timely regulation of M1-to-M2 polarization in tissue regeneration. These findings provide new insight to tissue healing of multiple tissues.

Identification of Osteosarcopenia by High-Resolution Peripheral Quantitative Computed Tomography

Osteosarcopenia is a prevalent geriatric disease with a significantly increased risk of adverse outcomes than osteoporosis or sarcopenia alone. Identification of older adults with osteosarcopenia using High-Resolution Peripheral Quantitative Computed Tomography (HR-pQCT) could allow better clinical decision making. This study aimed to explore the feasibility of HR-pQCT to differentiate osteoporosis, sarcopenia, and osteosarcopenia in older adults, with a primary outcome to derive a model to distinguish older adults with osteosarcopenia from those with low bone mineral density only, and to examine important HR-pQCT parameters associated with osteosarcopenia. This was a cross-sectional study involving 628 community-dwelling Chinese adults aged ≥ 40. Subjects were assessed by dual energy X-ray absorptiometry (DXA) for osteopenia/osteoporosis and sarcopenia using the Asian Working Group for Sarcopenia definition; then grouped into healthy, osteopenia/osteoporosis, sarcopenia, and osteosarcopenia groups. A series of regression analyses and other statistical tests were performed to derive the model. HR-pQCT showed the ability to discriminate older adults with osteosarcopenia from those with osteopenia/osteoporosis only. Cross-validation of our derived model correctly classified 77.0% of the cases with good diagnostic power and showed a sensitivity of 76.0% and specificity of 77.6% (Youden index = 0.54; AUC = 0.79, p < 0.001). Analysis showed trabecular volumetric bone density and cortical periosteal perimeter were important and sensitive parameters in discriminating osteosarcopenia from osteopenia/osteoporosis subjects. These findings demonstrated that HR-pQCT is a viable and effective screening method for differentiating osteosarcopenia from low bone mineral density alone without the need to carry out multiple assessments for osteosarcopenia, especially for case-finding purposes. This could facilitate the decision of a follow-up and the management of these frail older adults to ensure they receive timely therapeutic interventions to minimise the associated risks.

Sarcopenic obesity defined by the ESPEN and EASO consensus statement in older women: Risk of falls and bone mineral density implications

PURPOSE

To apply the ESPEN-EASO diagnostic criteria for Sarcopenic Obesity (SO) in older women and to assess its association with the risk of falls, fear of falls (FOF), and bone mineral density (BMD).

METHODS

After exclusion criteria, 232 women aged ≥60 years (68.2 ± 6.1) were enrolled in the study. Volunteers had handgrip strength (HGS; dynamometer) and body composition assessed by DXA before risk of falls was evaluated using the QuickScreen and FOF evaluated by the Falls Efficiency Scale. SO was defined according to the ESPEN-EASO algorithm, which includes reduced HGS and fat-free mass, and elevated fat mass.

RESULTS

The prevalence of SO was 6.5 %, which was associated with a higher proportion of fallers in the previous year (X2 6.2, P = 0.04), reduced reaction time (X2 6.2, P = 0.04), reduced sit-to-stand performance (X2 6.2, P = 0.04), and a higher probability of falls [ꭓ2(6) = 17.689, p = 0.004]. FOF was lower in the eutrophic group (ꭓ2(2) = 15,662, p < 0,001) than both the obesity (p = 0.001) and SO (p = 0.05) groups. For total and femoral neck BMD, the eutrophic group presented significantly lower values (1.05 and 0.79 g/cm2) than the obesity group (1.10 and 0.87 g/cm2), but similar to the SO group (1.02 and 0.83 g/cm2). These results remained significant after adjustments for potential confounders.

CONCLUSIONS

SO specified by the ESPEN-EASO framework was associated with a higher risk of falls but not with increased FOF than obesity alone. The favorable influence of overweight and obesity on BMD seems to be attenuated in individuals with SO. Our findings support the clinical significance of the ESPEN-EASO definition.

Myokines: A central point in managing redox homeostasis and quality of life

Redox homeostasis is a crucial phenomenon that is obligatory for maintaining the healthy status of cells. However, the loss of redox homeostasis may lead to numerous diseases that ultimately result in a compromised quality of life. Skeletal muscle is an endocrine organ that secretes hundreds of myokines. Myokines are peptides and cytokines produced and released by muscle fibers. Skeletal muscle secreted myokines act as a robust modulator for regulating cellular metabolism and redox homeostasis which play a prime role in managing and improving metabolic function in multiple organs. Further, the secretory myokines maintain redox homeostasis not only in muscles but also in other organs of the body via stabilizing oxidants and antioxidant levels. Myokines are also engaged in maintaining mitochondrial dynamics as mitochondria is a central point for the generation of reactive oxygen species (ROS). Ergo, myokines also act as a central player in communicating signals to other organs, including the pancreas, gut, liver, bone, adipose tissue, brain, and skin via their autocrine, paracrine, or endocrine effects. The present review provides a comprehensive overview of skeletal muscle-secreted myokines in managing redox homeostasis and quality of life. Additionally, probable strategies will be discussed that provide a solution for a better quality of life.

The prevalence of sarcopenia and risk factors in the older adult in China: a systematic review and meta-analysis

Background

Understanding the epidemiological information of a certain disease is the first step in related prevention and control work. This article aims to understand the prevalence and associated risk factors of sarcopenia among the older adult (≥60 years old) in China and to provide an evidence-based basis for early identification, management, and prevention of sarcopenia patients.

Methods

We searched seven databases: CNKI, Wanfang, VIP, PubMed, Web of Science, Embase, and Cochrane Library databases from the establishment of the database until January 31, 2024. The Quality evaluation criteria of cross-sectional studies recommended by the Agency for Healthcare Research and Quality (AHRQ) were used for literature quality evaluation. Stata 18.0 software was used for statistical analysis.

Results

We finally included 45 studies, involving a total of 37,571 cases. After statistical analysis, we found that the prevalence of sarcopenia among the older adult in China was 20.7% [95% CI (18.3, 23.0%)]. The results of subgroup analysis suggest that: ① According to gender, the prevalence rate of sarcopenia in women (21.6%) is higher than that in men (19.2%); ② According to age, the prevalence rate of older adult people aged ≥80 (45.4%) was the highest, followed by 70-79 (27.2%) and 60-69 (15.7%). ③ According to region, the prevalence rate of the older adult in the south (21.7%) is higher than that in the north (19.0%); ④ According to the time of publication, the prevalence of sarcopenia among the older adult in China has increased (from 19.2% in 2014-2018 to 21.4% in 2019-2024); ⑤ According to the diagnostic criteria, the detection rate of AWGS (2019) is higher than that of AWGS (2014) (24.5% vs. 19.3%). Finally, aging, low BMI, low leg circumference, smoking, depression, osteoporosis, malnutrition and malnutrition risk are all risk factors for sarcopenia among the older adult in China.

Conclusion

The prevalence of sarcopenia in the older adult in China was higher (20.7%), which should be paid attention to by relevant health authorities. In addition, aging, low BMI, low calf circumference, smoking, depression, osteoporosis, malnutrition and malnutrition risk are risk factors for the development of sarcopenia in the older adult in China. For these high-risk populations, early identification, prevention, and intervention can be carried out to delay the occurrence and progression of sarcopenia.

Extracellular vesicles may provide an alternative detoxification pathway during skeletal muscle myoblast ageing

Skeletal muscle (SM) acts as a secretory organ, capable of releasing myokines and extracellular vesicles (SM-EVs) that impact myogenesis and homeostasis. While age-related changes have been previously reported in murine SM-EVs, no study has comprehensively profiled SM-EV in human models. To this end, we provide the first comprehensive comparison of SM-EVs from young and old human primary skeletal muscle cells (HPMCs) to map changes associated with SM ageing. HPMCs, isolated from young (24 ± 1.7 years old) and older (69 ± 2.6 years old) participants, were immunomagnetically sorted based on the presence of the myogenic marker CD56 (N-CAM) and cultured as pure (100% CD56+) or mixed populations (MP: 90% CD56+). SM-EVs were isolated using an optimised protocol combining ultrafiltration and size exclusion chromatography (UF + SEC) and their biological content was extensively characterised using Raman spectroscopy (RS) and liquid chromatography mass spectrometry (LC-MS). Minimal variations in basic EV parameters (particle number, size, protein markers) were observed between young and old populations. However, biochemical fingerprinting by RS highlighted increased protein (amide I), lipid (phospholipids and phosphatidylcholine) and hypoxanthine signatures for older SM-EVs. Through LC-MS, we identified 84 shared proteins with functions principally related to cell homeostasis, muscle maintenance and transcriptional regulation. Significantly, SM-EVs from older participants were comparatively enriched in proteins involved in oxidative stress and DNA/RNA mutagenesis, such as E3 ubiquitin-protein ligase TTC3 (TTC3), little elongation complex subunit 1 (ICE1) and Acetyl-CoA carboxylase 1 (ACACA). These data suggest SM-EVs could provide an alternative pathway for homeostasis and detoxification during SM ageing.

Wnt/β-catenin signaling pathway as an important mediator in muscle and bone crosstalk: A systematic review

Background

The interaction between muscle and bone is shown to be clinically important but the underlying mechanisms are largely unknown. The canonical Wnt/β-catenin signaling pathway is reported to be involved in muscle-bone crosstalk, but its detailed function remains unclear. This systematic review aims to investigate and elucidate the role of the Wnt/β-catenin signaling pathways in muscle-bone crosstalk.

Methods

We conducted a literature search on the Web of Science, PubMed, EBSCO and Embase with keywords "Wnt*", "bone*" and "muscle*". A systematic review was completed according to the guideline of preferred reporting items of systematic reviews and meta-analyses (PRISMA). Data synthesis included species (human, animal or cell type used), treatments involved, outcome measures and key findings with respect to Wnts.

Results

Seventeen papers were published from 2007 to 2021 and were extracted from a total of 1529 search results in the databases of Web of Science (468 papers), PubMed (457 papers), EBSCO (371) and Embase (233). 12 Wnt family members were investigated in the papers, including Wnt1, Wnt2, Wnt2b, Wnt3a, Wnt4, Wnt5a, Wnt8a, Wnt8b, Wnt9a, Wnt10a, Wnt10b and Wnt16. Many studies showed that muscles were able to increase or decrease osteogenesis of bone, while bone increased myogenesis of muscle through Wnt/β-catenin signaling pathways. Wnt3a, Wnt4 and Wnt10b were shown to play important roles in the crosstalk between muscle and bone.

Conclusions

Wnt3a, Wnt4 and Wnt10b are found to play important mediatory roles in muscle-bone crosstalk. The role of Wnt4 was mostly found to regulate muscle from the bone side. Whilst the role of Wnt10b during muscle ageing was proposed, current evidence is insufficient to clarify the specific role of Wnt/β-catenin signaling in the interplay between sarcopenia and osteoporosis. More future studies are required to investigate the exact regulatory roles of Wnts in muscle-bone crosstalk in musculoskeletal disease models such as sarcopenia and osteoporosis.

Translational potential of this article

The systematic review provides an extensive overview to reveal the roles of Wnt/β-catenin signaling pathways in muscle-bone crosstalk. These results provide novel research directions to further understand the underlying mechanism of sarcopenia, osteoporosis, and their crosstalk, finally helping the future development of new therapeutic interventions.

The Function and Mechanism of Anti-Inflammatory Factor Metrnl Prevents the Progression of Inflammatory-Mediated Pathological Bone Osteolytic Diseases

Metrnl, recently identified as an adipokine, is a secreted protein notably expressed in white adipose tissue, barrier tissues, and activated macrophages. This adipokine plays a pivotal role in counteracting obesity-induced insulin resistance. It enhances adipose tissue functionality by promoting adipocyte differentiation, activating metabolic pathways, and exerting anti-inflammatory effects. Extensive research has identified Metrnl as a key player in modulating inflammatory responses and as an integral regulator of muscle regeneration. These findings position Metrnl as a promising biomarker and potential therapeutic target in treating inflammation-associated pathologies. Despite this, the specific anti-inflammatory mechanisms of Metrnl in immune-mediated osteolysis and arthritis remain elusive, warranting further investigation. In this review, we will briefly elaborate on the role of Metrnl in anti-inflammation function in inflammation-related osteolysis, arthritis, and pathological bone resorption, which could facilitate Metrnl's clinical application as a novel therapeutic strategy to prevent bone loss. While the pathogenesis of elbow stiffness remains elusive, current literature suggests that Metrnl likely exerts a pivotal role in its development.

Interrelationships between sarcopenia, bone turnover markers and low bone mineral density in patients on hemodialysis

BACKGROUND

Hemodialysis (HD) patients are at risk for sarcopenia (SP) and bone loss, which may impact falls and bone fragility and lead to poor prognosis. Patients with HD and those with osteoporosis (OP) are still underdiagnosed and untreated. The aims of the present study were to evaluate the factors that affect bone mineral density (BMD) loss in HD patients, and explore traditional and novel approaches to manage chronic kidney disease-mineral-bone disorder (CKD-MBD).

METHODS

Patients who underwent regular HD at the First Affiliated Hospital of Soochow University were retrospectively evaluated. According to the WHO osteoporosis criteria, patients were categorized into three groups: normal BMD, osteopenia, and osteoporosis. Demographic and clinical data, skeletal muscle mass, and bone turnover markers(BTM) were compared between the three groups. The correlation between bone density and muscle mass was calculated, and related risk factors were analyzed.

RESULTS

This study enrolled 130 HD patients, 36 patients were diagnosed with sarcopenia (27.7%), 44 patients were diagnosed with osteopenia (33.8%), 19 patients were diagnosed with osteoporosis (14.6%), and 23 patients were diagnosed with osteosarcopenia (17.7%). The SMI was positively correlated with the BMD of the lumbar spine (r = 0.23, p < 0.01) and femoral neck (r = 0.22, p < 0.05). In ordinal logistic regression analysis, the odds ratio (OR) for low BMD was high for patients with sarcopenia (OR = 5.894, 95% CI 1.592-21.830, p < 0.01), older age (OR = 1.095, 95% CI 1.041-1.153, p < 0.001), higher TRACP-5b levels (OR = 1.597, 95% CI 1.230-2.072, p < 0.01), and lower 25-OH vitamin D levels (OR = 0.631, 95% CI 0.544-0.733, p < 0.001).

CONCLUSION

The preservation of skeletal muscle mass could be important to prevent a BMD decrease in HD patients. Adequate intake of vitamin D and control of TRACP-5b levels will help reduce the occurrence and progression of osteopenia/sarcopenia in HD patients.

Effect of regional body composition changes on bone density remodeling after sleeve gastrectomy

Background

Sleeve gastrectomy (SG) results in bone mineral density (BMD) loss and varying body composition parameters. However, the effects of body compositions on bone health are controversial. In order to accurately demonstrate their relationship and provide new insights into the causes of BMD loss after sleeve gastrectomy, this study is aimed to investigate the role of changes in body composition in BMD loss 12 months after SG.

Methods

41 Chinese individuals with obesity (25 women and 16 men) who underwent SG were prospectively examined for at least 12 months. Measurements of anthropometrics, body composition, BMD and blood samples were collected.

Results

For 12 months, the femoral neck (FN) BMD and total hip (TH) BMD decreased significantly compared with baseline in both sexes but not lumbar spine (LS) BMD. Greater TH BMD loss was observed in men than in women. For the first 6 months post-SG, the FN BMD loss was positively associated with the estimated fat free mass index (eFFMI) reduction in women (adjusted β = 0.77, P = 0.004) and positively associated with reduction of subcutaneous fat area (SFA) in men (r = 0.931, P = 0.007). For 12 months post-SG, the FN BMD loss was negatively associated with visceral fat area (VFA) reduction in women (adjusted β = -0.58, P = 0.027) and men (adjusted β = -0.68, P = 0.032). TH BMD loss was positively associated with waist circumference reduction in women (r = 0.448, P = 0.028).

Conclusion

FN and TH BMD decrease after SG in both women and men. The changes in body compositions are associated with BMD loss at different time points and bone sites. Our data emphasize the limitation of simply taking the total weight loss (% TWL) as an influencing factor of bone mineral density and the necessity of delineating body composition in relevant studies.

Age, body composition parameters and glycaemic control contribute to trabecular bone score deterioration in acromegaly more than disease activity

Introduction

Impairment of bone structure in patients with acromegaly (AP) varies independently of bone mineral density (BMD). Body composition parameters, which are altered in patients with acromegaly, are important determinants of bone strength.

Purpose

The aim of this study was to examine BMD and lumbar trabecular bone score (TBS) by dual-energy X-ray absorptiometry (DXA) and to assess its relationship with disease activity, age, glucose metabolism, and body composition parameters.

Methods

This cross-sectional prospective study involved 115 patients with acromegaly (70 F, 45 M) and 78 healthy controls (CON) (53 F, 25 M) matched for age, gender, and BMI. Bone mineral density, TBS and body composition parameters were measured using DXA.

Results

AP presented with lower TBS compared to CON (1.2 ± 0.1 v 1.31 ± 0.1, P< 0.001). No significant correlation was observed between IGF-1/GH levels and TBS. Age, glycated haemoglobin, BMI, waist circumference, fat mass, and lean mass negatively correlated with TBS in both sexes. Multiple linear regression analysis of all these parameters revealed age and waist circumference as independent significant predictors of TBS in AP. We did not find difference in BMD (lumbar and femoral sites) between AP and CON nor between active and controlled AP. We observed negative correlation between age and BMD of the femoral neck and total hip (P < 0.001). Testosterone levels in males, BMI, waist circumference, fat mass, and lean mass positively correlated with BMD in AP, with stronger correlation between lean mass and BMD compared to fat mass.

Conclusion

Patients with acromegaly have lower TBS than controls, confirming impaired bone microarchitecture in acromegaly regardless of BMD. Age, body composition parameters and glucose metabolism contribute to TBS deterioration in AP more than disease activity itself.

Prevalence and risk factors of osteosarcopenia: a systematic review and meta-analysis

BACKGROUND

Osteosarcopenia is a syndrome with a concomitant presence of both sarcopenia and osteopenia/osteoporosis. It increases the risk of frailty, falls, fractures, hospitalization, and death. Not only does it burden the lives of older adults, but it also increases the economic burden on health systems around the world. This study aimed to review the prevalence and risk factors of osteosarcopenia to generate important references for clinical work in this area.

METHODS

Pubmed, Embase, Cochrane Library, Web of Science, CNKI, Wanfang, CBM, and VIP databases were searched from inception until April 24th, 2022. The quality of studies included in the review was evaluated using the NOS and AHRQ Scale. Pooled effects of the prevalence and associated factors were calculated using random or fixed effects models. Egger's test, Begg's test, and funnel plots were used to test the publication bias. Sensitivity analysis and subgroup analysis were conducted to identify the sources of heterogeneity. Statistical analysis was performed using Stata 14.0 and Review Manager 5.4.

RESULTS

A total of 31 studies involving 15,062 patients were included in this meta-analysis. The prevalence of osteosarcopenia ranged from 1.5 to 65.7%, with an overall prevalence of 21% (95% CI: 0.16-0.26). The risk factors for osteosarcopenia were female (OR 5.10, 95% CI: 2.37-10.98), older age (OR 1.12, 95% CI: 1.03-1.21), and fracture (OR 2.92, 95% CI: 1.62-5.25).

CONCLUSION

The prevalence of osteosarcopenia was high. Females, advanced age, and history of fracture were independently associated with osteosarcopenia. It is necessary to adopt integrated multidisciplinary management.

A spike in circulating cytokines TNF-α and TGF-β alters barrier function between vascular and musculoskeletal tissues

Molecular transport between the circulatory and musculoskeletal systems regulates articular joint physiology in health and disease. Osteoarthritis (OA) is a degenerative joint disease linked to systemic and local inflammation. Inflammatory events involve cytokines, which are secreted by cells of the immune system and modulate molecular transport across tissue interfaces (referred to as tight junction [TJ] barrier function). In a previous study from our group, OA knee joint tissues were shown to exhibit size separation of different sized molecules delivered as a single bolus to the heart (Ngo et al. in Sci. Rep. 8:10254, 2018). Here, in a follow up study of parallel design, we test the hypothesis that two common cytokines, with multifaceted roles in the etiology of osteoarthritis as well as immune state in general, modulate the barrier function properties of joint tissue interfaces. Specifically, we probe the effect of an acute cytokine increase (spike) on molecular transport within tissues and across tissue interfaces of the circulatory and musculoskeletal systems. A single bolus of fluorescent-tagged 70 kDa dextran, was delivered intracardially, either alone, or with either the pro-inflammatory cytokine TNF-α or the anti-inflammatory cytokine TGF-β, to skeletally mature (11 to 13-month-old) guinea pigs (Dunkin-Hartley, a spontaneous OA animal model). After five minutes' circulation, whole knee joints were serial sectioned and fluorescent block face cryo-imaged at near-single-cell resolution. The 70 kDa fluorescent-tagged tracer is analogous in size to albumin, the most prevalent blood transporter protein, and quantification of tracer fluorescence intensity gave a measure of tracer concentration. Within five minutes, a spike (acute doubling) in circulating cytokines TNF-α or TGF-β significantly disrupted barrier function between the circulatory and musculoskeletal systems, with barrier function essentially abrogated in the TNF-α group. In the entire volume of the joint (including all tissue compartments and the bounding musculature), tracer concentration was significantly decreased in the TGF-β- and TNF-α- compared to the control-group. These studies implicate inflammatory cytokines as gatekeepers for molecular passage within and between tissue compartments of our joints and may open new means to delay the onset and mitigate the progression of degenerative joint diseases such as OA, using pharmaceutical and/or physical measures.

All-trans Retinoic Acid and Beta-Carotene Increase Sclerostin Production in C2C12 Myotubes

Sclerostin is a protein secreted by osteocytes whose encoding gene SOST is regulated by mechanical stimuli, cytokines, and all-trans retinoic acid (ATRA) and mediates antianabolic effects on bone formation as an inhibitor of the canonical Wnt/β-catenin pathway. Interestingly, skeletal muscle has recently been identified as another source of sclerostin, suggesting that the musculature may play an important role in maintaining bone mass. However, regulators of muscular SOST expression are virtually unknown. This study investigates the influence of ATRA and the provitamin A derivative beta-carotene (β-C) on sclerostin synthesis in muscle cells. The impact of ATRA, its synthetic analog TTNPB, and β-C on Sost transcription was analyzed by qRT-PCR in C2C12 myotubes and the secreted sclerostin protein by ELISA. ATRA strongly increases the sclerostin synthesis in C2C12 myotubes in a dose-dependent manner. The stimulating effect of ATRA and TTNPB on Sost is largely reduced in the presence of the retinoic acid receptor inhibitor AGN193109. β-C also increases the Sost expression, but this effect vanishes when β-C is coincubated with beta-carotene 15,15'-monooxygenase 1 (BCMO1)-specific siRNA. Thus, ATRA is a potent stimulator of sclerostin release in muscle cells. β-C can also increase Sost mRNA abundance, but this effect depends on the conversion to a retinoid.

Cancer-associated cachexia - understanding the tumour macroenvironment and microenvironment to improve management

Cachexia is a devastating, multifactorial and often irreversible systemic syndrome characterized by substantial weight loss (mainly of skeletal muscle and adipose tissue) that occurs in around 50-80% of patients with cancer. Although this condition mainly affects skeletal muscle (which accounts for approximately 40% of total body weight), cachexia is a multi-organ syndrome that also involves white and brown adipose tissue, and organs including the bones, brain, liver, gut and heart. Notably, cachexia accounts for up to 20% of cancer-related deaths. Cancer-associated cachexia is invariably associated with systemic inflammation, anorexia and increased energy expenditure. Understanding these mechanisms is essential, and the progress achieved in this area over the past decade could help to develop new therapeutic approaches. In this Review, we examine the currently available evidence on the roles of both the tumour macroenvironment and microenvironment in cancer-associated cachexia, and provide an overview of the novel therapeutic strategies developed to manage this syndrome.

Integrating Untargeted and Targeted Metabolomics Coupled with Pathway Analysis Reveals Muscle Disorder in Osteoporosis on Orchiectomized Mice

Most osteoporosis (OP) fracture accidents in men are due not only to a low BMD but also because of unhealthy muscle support. However, there has been a limited number of reports about how muscle metabolism is disturbed by OP in males. In this work, a pathway analysis based on metabolomic research was carried out to fill this gap. A classical orchiectomy procedure was adapted to create an OP animal model. A micro-CT and pathological section were applied for a bone and muscle phenotype assessment and a pathology analysis. UPLC-Q-TOF/MS and UPLC-QQQ-MS/MS were applied to measure metabolites in skeletal muscle samples among groups. In total, 31 significantly differential metabolites were detected by comparing healthy models and OP animals, and 7 representative metabolites among the 31 significantly differential metabolites were identified and validated experimentally by UPLC-QQQ-MS/MS (xanthine, L-phenylalanine, choline, hypoxanthine, L-tryptophan, succinic acid, and L-tyrosine). An ingenuity pathway analysis (IPA) analysis revealed significantly enriched pathways involved in inflammation, oxidative stress, and necrosis. To our best knowledge, this is the first study to investigate early muscle disorder processes in Cases of OP at a metabolic level, facilitating early intervention and protection from OP fractures for aged men.

Muscle-derived extracellular vesicles improve disuse-induced osteoporosis by rebalancing bone formation and bone resorption

Osteoporosis is a highly prevalent skeletal bone disorder worldwide with characteristics of reduced bone mass and increased risk of osteoporotic fractures. It has been predicted to become a global challenge with the aging of the world population. However, the current therapy based on antiresorptive drugs and anabolic drugs has unwanted side effects. Although cell-based treatments have shown therapeutic effects for osteoporosis, there are still some limitations inhibiting the process of clinical application. In the present study, we developed EVs derived from skeletal muscle tissues (Mu-EVs) as a cell-free therapy to treat disuse-induced osteoporosis. Our results showed that Mu-EVs could be prepared easily and abundantly from skeletal muscle tissues, and that these Mu-EVs had typical features of extracellular vesicles. In vitro studies demonstrated that Mu-EVs from normal skeletal muscles could be phagocytized by bone marrow stromal/stem cells (BMSCs) and osteoclasts (OCs), and promoted osteogenic differentiation of BMSCs while inhibited OCs formation. Correspondingly, Mu-EVs from atrophic skeletal muscles attenuated the osteogenesis of BMSCs and strengthened the osteoclastogenesis of monocytes. In vivo experiments revealed that Mu-EVs could efficiently reverse disuse-induced osteoporosis by enhancing bone formation and suppressing bone resorption. Collectively, our results suggest that Mu-EVs may be a potential cell-free therapy for osteoporosis treatment. STATEMENT OF SIGNIFICANCE: Osteoporosis is a highly prevalent skeletal bone disorder worldwide and has become a global health concern with the aging of the world population. The current treatment for osteoporosis has unwanted side effects. Extracellular veiscles (EVs) from various cell sources are a promising candidate for osteoporosis treatment. In the present study, our team established protocols to isolate EVs from culture supernatant of skeletal muscles (Mu-EVs). Uptake of Mu-EVs by BMSCs and osteoclasts influences the balance of bone remodeling via promoting the osteogenic differentiation of BMSCs and inhibiting the osteoclasts formation of monocytes. In addition, exogenous Mu-EVs from normal skeletal muscles are proved to reverse the disuse-induced osteoporosis. We provide experimental evidence that Mu-EVs therapy is a potential cell-free platform for osteoporosis treatment towards clinical application.

Bone metabolism characteristics and gender differences in patients with COPD: a cross-sectional study

BACKGROUND

Gender differences in bone metabolism of people with chronic obstructive pulmonary disease (COPD) remain unclear. We aim to explore the characteristics of bone metabolism and its clinical significance for patients with COPD.

METHODS

A total of 564 cases (282 COPD cases and 282 controls) were preselected. Clinical and analytical characteristics of these cases were assessed. After excluding patients with other conditions known to disturb calcium metabolism, 333 patients (152 COPD cases and 181 controls) were identified. The medical records, indexes of bone turnover markers, serum calcium and phosphorus of the 333 patients were collected and their correlation was analyzed.

RESULTS

The 152 cases with COPD were 82.61 ± 7.745 years, 78.3% males, and the 181 age- and sex-matched control cases were 79.73 ± 11.742 years, 72.4% males. Levels of total procollagen type I amino-terminal propeptide (tPINP), osteocalcin (OC), serum calcium and phosphate were significantly lower (P < 0.001) while the level of parathormone (PTH) was significantly higher (P = 0.004) in COPD than in controls. The 25-hydroxycholecalciferol (25(OH)D₃) was below the lower limit of normal value (LLN) in both groups, which was significantly lower in COPD males than in control males (P = 0.026). In COPD group, PTH level was significantly higher in females (P = 0.006), and serum P was lower in males (P = 0.006). The adjusted linear regression analysis showed that the levels of tPINP, OC and serum Ca were decreasing greatly in COPD group [β (95%CI) - 8.958 (- 15.255 to - 2.662), P = 0.005; - 4.584 (- 6.627 to - 2.542), P < 0.001; - 0.065 (- 0.100 to - 0.031), P < 0.001]. Besides, smoke exposure, gender (male) were also related to hypocalcemia [β (95%CI) - 0.025 (- 0.045 to - 0.005), P = 0.017; - 0.041 (- 0.083 to - 0.001), P = 0.047], and 25(OH)D₃ was correlated with serum calcium, phosphorus, and PTH [β (95%CI) 15.392(7.032-23.753), P < 0.001; - 7.287 (- 13.450 to - 1.124), P = 0.021; - 0.103(- 0.145 to - 0.061), P < 0.001], and female was more likely to have secondary hyperparathyroidism [β (95%CI) 12.141 (4.047-20.235), P = 0.002].

CONCLUSION

COPD patients have remarkably low bone turnover (indicated by OC) and impaired bone formation (low tPINP), and they are also more prone to low calcium. Smoking and male may play roles in the formation of hypocalcemia, and the secondary hyperparathyroidism is more significant in COPD women. There may be gender differences in bone metabolism abnormalities and their mechanisms of COPD. The conclusion above still need further research and demonstration.

Skeletal Muscle's Role in Prenatal Inter-organ Communication: A Phenogenomic Study with Qualitative Citation Analysis

Gene targeting in mice allows for a complete elimination of skeletal (striated or voluntary) musculature in the body, from the beginning of its development, resulting in our ability to study the consequences of this ablation on other organs. Here I focus on the relationship between the muscle and lung, motor neurons, skeleton, and special senses. Since the inception of my independent laboratory, in 2000, with my team, we published more than 30 papers (and a book chapter), nearly 400 pages of data, on these specific relationships. Here I trace, using Web of Science, nearly 600 citations of this work, to understand its impact. The current report contains a summary of our work and its impact, NCBI's Gene Expression Omnibus accession numbers of all our microarray data, and three clear future directions doable by anyone using our publicly available data. Together, this effort furthers our understanding of inter-organ communication during prenatal development.

Precedence of Bone Loss Accompanied with Changes in Body Composition and Body Fat Distribution in Patients with Type 2 Diabetes Mellitus

Methods

A total of 596 patients with T2DM, including 308 male and 288 female patients, were included in the follow-up study; the median follow-up time was 2.17 years. We calculated the difference between the endpoint and the baseline of each body composition index and the annual rate. The research participants were divided into the increased body mass index (BMI) group, stable BMI group, and decreased BMI group. Some confounding factors were adjusted, such as BMI, fat mass index (FMI), muscle mass index (MMI), muscle/fat mass ratio (M/F), trunk fat mass index (TFMI), appendicular skeletal muscle mass index (ASMI), and appendicular skeletal muscle mass/trunk fat mass ratio (A/T).

Results

The linear analysis showed that ΔFMI and ΔTFMI were negatively correlated with the change in femoral neck BMD (ΔFNBMD) and ΔMMI, ΔASMI, ΔM/F, and ΔA/T were positively correlated with ΔFNBMD. The risk of FNBMD reduction in patients with increased BMI was 56.0% lower than that in patients with decreased BMI; also, the risk in patients with stable M/F was 57.7% lower than that in patients with decreased M/F. The risk in the A/T increase group was 62.9% lower than that in the A/T decrease group.

Conclusions

A reasonable muscle/fat ratio is still beneficial to maintaining bone mass. Maintaining a certain BMI value is conducive to maintaining FNBMD. Simultaneously, increasing the proportion of muscle mass and reducing fat accumulation can also prevent FNBMD loss.

Advancement in the Treatment of Osteoporosis and the Effects on Bone Healing

Osteoporosis (OP) is a major global health concern, with aging being one of the most important risk factors. Osteoarthritis (OA) is also an age-related disorder. Patients with OP and/or OA may be treated surgically for fractures or when their quality of life is impaired. Poor bone quality due to OP can seriously complicate the stability of a bone fixation construct and/or surgical fracture treatment. This review summarizes the current knowledge on the pathophysiology of normal and osteoporotic bone healing, the effect of a bone fracture on bone turnover markers, the diagnosis of a low bone mineral density (BMD) before surgical intervention, and the effect of available anti-osteoporosis treatment. Interventions that improve bone health may enhance the probability of favorable surgical outcomes. Fracture healing and the treatment of atypical femoral fractures are also discussed.

A pooled analysis of the association between sarcopenia and osteoporosis

BACKGROUND

Sarcopenia is a progressive generalized skeletal muscle disorder that causes the accelerated loss of muscle mass and function. Osteoporosis is a systemic condition of the skeleton that results in low bone mass and quality. Several studies have suggested that osteoporosis and sarcopenia are interrelated; however, a few studies indicate the lack of a significant association between sarcopenia and osteoporosis. We aimed to evaluate the association between sarcopenia and osteoporosis via a systematic review and pooled analysis.

METHODS

From the inception of the PubMed and Embase databases until September 2022, we conducted a systematic search for studies evaluating the relationship between sarcopenia and osteoporosis. Study appraisal and synthesis methods: We included observational studies that provided 95% confidence intervals (CIs) and risk estimates. Two reviewers independently extracted data and assessed the quality of the research. The random-effects model was applied to the pool analysis, and the odds ratios (ORs) and 95% CIs were finally calculated.

RESULTS

The primary statistic was the mutual risk between sarcopenia and osteoporosis. According to the inclusion criteria, 56 studies (796,914 participants) were finally included. Sarcopenia was significantly correlative to the risk of osteoporosis (OR, 3.06; 95% CI, 2.30-4.08), and each standard deviation increase in relative appendicular skeletal muscle mass was significantly related to a decreased risk of osteoporosis (OR, 0.65; 95% CI, 0.56-0.75). Osteoporosis observably referred to a higher risk of sarcopenia (OR, 2.63; 95% CI, 1.98-3.49).

CONCLUSION

Our research indicated that sarcopenia and osteoporosis are highly positively correlated. Osteoporosis is closely associated with the risk of sarcopenia. Our finding highlights the importance of sarcopenia screening for those at risk of osteoporosis, and vice versa. However, heterogeneity was noted among the studies, and this might have influenced the accuracy of the results. Therefore, the results of our study should be interpreted with caution.

Progression of microstructural deterioration in load-bearing immobilization osteopenia

Purpose

Immobilization osteopenia is a major healthcare problem in clinical and social medicine. However, the mechanisms underlying this bone pathology caused by immobilization under load-bearing conditions are not yet fully understood. This study aimed to evaluate sequential changes to the three-dimensional microstructure of bone in load-bearing immobilization osteopenia using a fixed-limb rat model.

Materials and method

Eight-week-old specific-pathogen-free male Wistar rats were divided into an immobilized group and a control group (n = 60 each). Hind limbs in the immobilized group were fixed using orthopedic casts with fixation periods of 1, 2, 4, 8, and 12 weeks. Feeding and weight-bearing were freely permitted. Length of the right femur was measured after each fixation period and bone microstructure was analyzed by micro-computed tomography. The architectural parameters of cortical and cancellous bone were analyzed statistically.

Results

Femoral length was significantly shorter in the immobilized group than in the control group after 2 weeks. Total area and marrow area were significantly lower in the immobilized group than in the control group from 1 to 12 weeks. Cortical bone area, cortical thickness, and polar moment of inertia decreased significantly after 2 weeks. Some cancellous bone parameters showed osteoporotic changes at 2 weeks after immobilization and the gap with the control group widened as the fixation period extended (P < 0.05).

Conclusion

The present results indicate that load-bearing immobilization triggers early deterioration of microstructure in both cortical and cancellous bone after 2 weeks.

Associations between Bone Mineral Density and Longitudinal Changes of Vertebral Bone Marrow and Paraspinal Muscle Composition Assessed Using MR-Based Proton Density Fat Fraction and T2* Maps in Patients with and without Osteoporosis

Background: Proton-density fat fraction (PDFF) and T2* of the vertebrae, as well as the cross-sectional area (CSA) of the paraspinal musculature (PSM), have been suggested as biomarkers for bone fragility. The aim of this study was to longitudinally assess changes in PDFF, T2* and CSA of the PSM over 6 months in patients with and without osteoporosis. Methods: Opportunistic bone mineral density (BMD) measurements (BMD < 120 mg/cm3) were obtained from a CT acquired during the clinical routine work up in osteoporotic/osteopenic patients (n = 29, mean age 72.37 ± 10.12 years, 16 women). These patients were frequency-matched for age and sex to subjects with normal BMD values (n = 29). All study patients underwent 3T MR imaging at baseline and 6-month follow up, including spoiled gradient echo sequences for chemical shift encoding-based water-fat separation, from which T2* and PDFF values of the lumbar spine and the PSM were obtained. Moreover, the CSA of the PSM was assessed longitudinally. Changes in T2*, PDFF and CSA over 6 months were calculated for the vertebrae and PSM and associations with baseline BMD values were assessed. Results: The change in CSA of the PSM over 6 months was significantly lower in the osteoporotic/osteopenic group (−91.5 ± 311.7 mm2), compared to the non-osteoporotic group, in which the CSA increased (29.9 ± 164.0 mm2, p = 0.03). In a further analysis, patients with higher vertebral PDFF at baseline showed a significantly stronger increase in vertebral T2*, compared to those patients with lower vertebral PDFF at baseline (0.9 ± 1.6 ms vs. 0.0 ± 1.8 ms, p = 0.04). Moreover, patients with higher PSM PDFF at baseline showed a significantly stronger increase in vertebral T2*, compared to those patients with lower PSM PDFF at baseline (0.9 ± 2.0 ms vs. 0.0 ± 1.3 ms, p = 0.03). Conclusion: The PSM CSA decreased significantly longitudinally in patients with osteoporosis/osteopenia, compared to those without. Additionally, higher vertebral and PSM PDFF at baseline were associated with stronger changes in vertebral bone marrow T2*. Therefore, longitudinal PDFF and T2* mapping may be useful quantitative radiation-free tools for the assessment and prediction of muscle and bone health in patients with suspected osteoporosis/osteopenia.

miR21 deletion in osteocytes has direct and indirect effects on skeletal muscle in a sex-dimorphic manner in mice

Background

Osteocytic microRNA21 (miR21) removal alters cytokine production and bone mass by modulating osteoclast and osteoblast differentiation and activity. Removing osteocytic miR21 increases osteoclast/osteoblast numbers and bone mass in male mice, whereas it decreases osteoclasts/osteoblasts without affecting bone mass in female mice. On the other hand, it leads to sex-independent increases in bone mechanical properties. Because changes in bone remodeling and strength affect skeletal muscle through bone–muscle crosstalk, we investigated whether osteocytic miR21 deletion influences skeletal muscle.

Methods

miR21fl/fl mice and 8kbDMP1-Cre mice were mated to obtain miR21-deficient mice primarily in the osteocyte (OtmiR21Δ) and littermate controls (miR21fl/fl). Four-month-old male and female mice were analyzed. Body composition was examined by DXA/Piximus and gene expression was assessed by qPCR. Ex vivo cultures of long bones devoid of bone-marrow cells from male and female 4-month-old were maintained for 48 h. Conditioned media were collected and used for the C2C12 assays. Two-way ANOVA analyses were performed to determine the contributions of genotype and sex and their interaction to the effects of miR21 deficiency.

Results

Lean body mass was increased only in female OtmiR21Δ mice, although miR21 levels in soleus muscle were similar in miR21fl/fl (0.05 ± 0.02) and OtmiR21Δ (0.09 ± 0.04) mice. Female, but not male, OtmiR21Δ mice exhibited increased soleus (42%) and gastrocnemius (21%) muscle weight compared to miR21fl/fl littermates. However, muscle strength and gastrocnemius muscle fiber cross-sectional area were unaltered for either sex. Kinase phosphorylation (phospho/total protein ratio) in soleus muscle, measured as a surrogate for kinase activity by means of multiplex analysis, was also selectively changed depending on the mouse sex. Thus, female OtmiR21Δ mice had higher T185/Y187-ERK1/2 but lower S473-Akt phosphorylation than miR21fl/fl controls, while male OtmiR21Δ mice had higher S473-Akt phosphorylation, suggesting sex-dimorphic shifts in anabolic vs. catabolic signaling. Consistently, levels of FOXO3 and MuRF-1, known to be regulated by Akt, were only increased in male OtmiR21Δ mice. Atrogin-1 mRNA levels were upregulated in female OtmiR21Δ mice, suggesting a potential shift in protein regulation. Sex-specific effects were also found by exposing myotube cultures to conditioned media from 48-h-cultured marrow-flushed bones. Thus 5-day differentiated C2C12 myotubes treated with conditioned media of female OtmiR21Δ mice exhibit 12% higher average diameter compared to cells exposed to miR21fl/fl bone conditioned media. Yet, conditioned media from male bones had no effect on myotube size.

Conclusions

We present a novel aspect of bone–muscle crosstalk in which osteocyte-derived miR21 influences skeletal muscle size, but not strength, in female but not male mice; whereas, intracellular signaling alterations resulting from loss of miR21 seem to alter protein dynamics in a sex-dimorphic fashion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13293-022-00465-9.

Osteocytic microRNA21 (miR21) removal in OtmiR21Δ mice alters cytokine production and bone mass by modulating osteoclast and osteoblast differentiation and activity.

Only female, but not male, OtmiR21Δ mice exhibit higher lean body mass and soleus and gastrocnemius muscle weight compared to miR21fl/fl littermates.

Sex-dependent consequences of osteocytic miR21 deletion on skeletal muscle were also found at protein and gene expression level.

We conclude that osteocyte-derived miR21 influences skeletal muscle size, but not strength, in female but not male mice; whereas, intracellular signaling alterations resulting from loss of miR21 seem to alter protein dynamics in a sex-dimorphic fashion.

The Positive Association between Muscle Mass and Bone Status Is Conserved in Men with Diabetes: A Retrospective Cross-Sectional and Longitudinal Study

Bone and muscle are known to be correlated and interact chemically each other. Diabetes affects the health status of these two types of organ. There has been lack of studies of men on this topic. This study aims to investigate the relationship between bone and muscle status in men with and without diabetes. This study enrolled 318 and 88 men with and without diabetes, respectively, between April 2007 and December 2017. The appendicular skeletal muscle index (ASMI) was correlated with femoral neck bone mineral density (BMD), total hip BMD, and the trabecular bone score (TBS) in both groups (p < 0.001−0.008). In analysis of the changes in muscle mass and bone-related parameters over the 3 years, the ASMI was correlated with total hip BMD only in diabetes group (p = 0.016) and the TBS in both groups (p < 0.001−0.046). This study showed that the positive correlation between muscle mass and bone status was largely conserved in diabetic group in men. Moreover, in a long-term perspective, muscle mass might be more correlated with the bone microarchitecture or bone quality than bone density, and the association between muscle mass and total hip BMD could be stronger in the diabetic group.

Mechanical Disturbance of Osteoclasts Induces ATP Release That Leads to Protein Synthesis in Skeletal Muscle through an Akt-mTOR Signaling Pathway

Muscle and bone are tightly integrated through mechanical and biochemical signals. Osteoclasts are cells mostly related to pathological bone loss; however, they also start physiological bone remodeling. Therefore, osteoclast signals released during bone remodeling could improve both bone and skeletal muscle mass. Extracellular ATP is an autocrine/paracrine signaling molecule released by bone and muscle cells. Then, in the present work, it was hypothesized that ATP is a paracrine mediator released by osteoclasts and leads to skeletal muscle protein synthesis. RAW264.7-derived osteoclasts were co-cultured in Transwell^® chambers with flexor digitorum brevis (FDB) muscle isolated from adult BalbC mice. The osteoclasts at the upper chamber were mechanically stimulated by controlled culture medium perturbation, resulting in a two-fold increase in protein synthesis in FDB muscle at the lower chamber. Osteoclasts released ATP to the extracellular medium in response to mechanical stimulation, proportional to the magnitude of the stimulus and partly dependent on the P2X₇ receptor. On the other hand, exogenous ATP promoted Akt phosphorylation (S473) in isolated FDB muscle in a time- and concentration-dependent manner. ATP also induced phosphorylation of proteins downstream Akt: mTOR (S2448), p70S6K (T389) and 4E-BP1 (T37/46). Exogenous ATP increased the protein synthesis rate in FDB muscle 2.2-fold; this effect was blocked by Suramin (general P2X/P2Y antagonist), LY294002 (phosphatidylinositol 3 kinase inhibitor) and Rapamycin (mTOR inhibitor). These blockers, as well as apyrase (ATP metabolizing enzyme), also abolished the induction of FDB protein synthesis evoked by mechanical stimulation of osteoclasts in the co-culture model. Therefore, the present findings suggest that mechanically stimulated osteoclasts release ATP, leading to protein synthesis in isolated FDB muscle, by activating the P2-PI3K-Akt-mTOR pathway. These results open a new area for research and clinical interest in bone-to-muscle crosstalk in adaptive processes related to muscle use/disuse or in musculoskeletal pathologies.

Disuse Osteoporosis: Clinical and Mechanistic Insights

Disuse osteoporosis describes a state of bone loss due to local skeletal unloading or systemic immobilization. This review will discuss advances in the field that have shed light on clinical observations, mechanistic insights and options for the treatment of disuse osteoporosis. Clinical settings of disuse osteoporosis include spinal cord injury, other neurological and neuromuscular disorders, immobilization after fractures and bed rest (real or modeled). Furthermore, spaceflight-induced bone loss represents a well-known adaptive process to microgravity. Clinical studies have outlined that immobilization leads to immediate bone loss in both the trabecular and cortical compartments accompanied by relatively increased bone resorption and decreased bone formation. The fact that the low bone formation state has been linked to high levels of the osteocyte-secreted protein sclerostin is one of the many findings that has brought matrix-embedded, mechanosensitive osteocytes into focus in the search for mechanistic principles. Previous basic research has primarily involved rodent models based on tail suspension, spaceflight and other immobilization methods, which have underlined the importance of osteocytes in the pathogenesis of disuse osteoporosis. Furthermore, molecular-based in vitro and in vivo approaches have revealed that osteocytes sense mechanical loading through mechanosensors that translate extracellular mechanical signals to intracellular biochemical signals and regulate gene expression. Osteocytic mechanosensors include the osteocyte cytoskeleton and dendritic processes within the lacuno-canalicular system (LCS), ion channels (e.g., Piezo1), extracellular matrix, primary cilia, focal adhesions (integrin-based) and hemichannels and gap junctions (connexin-based). Overall, disuse represents one of the major factors contributing to immediate bone loss and osteoporosis, and alterations in osteocytic pathways appear crucial to the bone loss associated with unloading.

Exercised accelerated the production of muscle-derived kynurenic acid in skeletal muscle and alleviated the postmenopausal osteoporosis through the Gpr35/NFκB p65 pathway

Background

Reduced serum estrogen levels in postmenopausal patients not only aggravate bone loss but also impact myokine secretion. Emerging evidence has revealed the importance of myokines in bone metabolism, and exercise can interfere with the secretion of myokines. However, few studies have explored the impact of exercise on myokine secretion in the postmenopausal osteoporosis (PMOP) process.

Methods

Ten-weeks-old C57B/L6 female mice were used for constructing the postmenopausal osteoporosis model. The expression levels of kynurenine aminotransferases (Kats) were detected by RT-PCR and Western Blot. The concentration of serum kynurenic acid (Kyna) was detected by HPLC-MS. Micro-CT analysis was used for determine the changes of bone mineral density and the microstructure. The primary osteoblast and osteoclast were isolated from mice to determine the effect and mechanism of Kyna on the bone formation and resorption.

Results

In our research, we found a lower serum level of muscle-derived kynurenic acid (Kyna) in PMOP model mice, accompanied by a decreased level of kynurenine aminotransferases (Kats) in the gastrocnemius muscle. Moreover, treadmill-running exercise upregulated the muscle levels of KATs and increased the serum concentration of Kyna, which was positively correlated with the alleviation of bone loss. Furthermore, we found that exogenous Kyna treatment alleviated bone mineral loss and microstructure destruction in PMOP mice by inhibiting osteoclast maturation and increasing osteoblast viability. Mechanistically, we observed that Kyna reduced the NFκB p65 phosphorylation level by activating the Gpr35 receptor, which inhibited NFATc1 expression in osteoclasts and upregulated Runx2 expression in osteoblasts.

Conclusion

Our results revealed that the muscle levels of Kats and serum level of Kyna were negatively correlated with the severity of PMOP. Exercise intervention and exogenous Kyna treatment alleviated the impairment of bone microstructure through the Gpr35 receptor, paving the way for a novel therapeutic intervention in PMOP.

The Translational potential of this article

This study provides evidences that Kyna could increase the osteoblastgenesis and inhibit the osteoclastgenesis, which could be a novel therapeutic approach for osteoporosis treatment.

Sex differences in systemic bone and muscle loss following femur fracture in mice

Fracture induces systemic bone loss in mice and humans, and a first (index) fracture increases the risk of future fracture at any skeletal site more in men than women. The etiology of this sex difference is unknown, but fracture may induces a greater systemic bone loss response in men. Also sex differences in systemic muscle loss after fracture have not been examined. We investigated sex differences in systemic bone and muscle loss after transverse femur fracture in 3-month-old male and female C57BL/6 J mice. Whole-body and regional bone mineral content and density (BMC and BMD), trabecular and cortical bone microstructure, muscle contractile force, muscle mass, and muscle fiber size were quantified at multiple time points postfracture. Serum concentrations of inflammatory cytokines (IL-1β, IL-6, and TNF-α) were measured 1-day postfracture. One day postfracture, IL-6 and Il-1B were elevated in fracture mice of both sexes, but TNF-α was only elevated in male fracture mice. Fracture reduced BMC, BMD, and trabecular bone microstructural properties in both sexes 2 weeks postfracture, but declines were greater in males. Muscle contractile force, mass, and fiber size decreased primarily in the fractured limb at 2 weeks postfracture and females showed a trend toward greater muscle loss. Bone and muscle properties recovered by 6 weeks postfracture. Overall, postfracture systemic bone loss is greater in men, which may contribute to sex differences in subsequent fracture risk. In both sexes, muscle loss is primarily confined to the injured limb and fracture may induce greater inflammation in males.

Emerging cross-talks between chronic kidney disease-mineral and bone disorder (CKD-MBD) and malnutrition-inflammation complex syndrome (MICS) in patients receiving dialysis

Chronic kidney disease–mineral and bone disorder (CKD–MBD) is a systemic disorder that affects multiple organs and systems and increases the risk of morbidity and mortality in patients with CKD, especially those receiving dialysis therapy. CKD–MBD is highly prevalent in CKD patients, and its treatment is gaining attention from healthcare providers who manage these patients. Additional important pathologies often observed in CKD patients are chronic inflammation and malnutrition/protein-energy wasting (PEW). These two pathologies coexist to form a vicious cycle that accelerates the progression of various other pathologies in CKD patients. This concept is integrated into the term “malnutrition–inflammation–atherosclerosis syndrome” or “malnutrition–inflammation complex syndrome (MICS)”. Recent basic and clinical studies have shown that CKD–MBD directly induces inflammation as well as malnutrition/PEW. Indeed, higher circulating levels of inorganic phosphate, fibroblast growth factor 23, parathyroid hormone, and calciprotein particles, as markers for critical components and effectors of CKD–MBD, were shown to directly induce inflammatory responses, thereby leading to malnutrition/PEW, cardiovascular diseases, and clinically relevant complications. In this short review, we discuss the close interplay between CKD–MBD and MICS and emphasize the significance of simultaneous control of these two seemingly distinct pathologies in patients with CKD, especially those receiving dialysis therapy, for better management of the CKD/hemodialysis population.

The Role of Bone Muscle Ring Finger-1 (MuRF1), MuRF2, MuRF3, and Atrogin-1 on Microarchitecture In Vivo

Ubiquitin proteasome system was found to contribute to bone loss by regulating bone turnover and metabolism, by modulating osteoblast differentiation and bone formation as well as formation of osteoclasts that contribute to bone resorption. Muscle Ring Finger (MuRF) are novel ubiquitin ligases, which are muscle specific and have not been much implicated in the bone but have been implicated in several human diseases including heart failure and skeletal muscle atrophy. This study is aimed at understanding the role of MuRF1, MuRF2, MuRF3 and Atrogin which are distinct MuRF family proteins in bone homeostasis. Wildtype, heterozygous and homozygous mice of each of the isoforms were used and the bone microarchitecture and mechanical properties were assessed using microCT and biomechanics. MuRF1 depletion was found to alter cortical properties in both males and females, but only trabecular spacing in the females. MuRF2 depletion let to no changes in the cortical and trabecular properties but change in the strain to yield in the females. Depletion of MuRF3 led to decrease in the cortical properties in the females and increase in the trabecular properties in the males. Atrogin depletion was found to reduce cortical properties in both males and females, whereas some trabecular properties were found to be reduced in the females. Each muscle-specific ligase was found to alter the bone structure and mechanical properties in a distinct a sex-dependent manner.

Body Composition as a Modulator of Bone Health Changes in Patients with Inflammatory Bowel Disease

Background: Bone impairment of multifactorial etiology is a common feature in inflammatory bowel disease (IBD). Body composition parameters, which might be selectively modified in these patients, are important determinants of bone strength. Our aim was to investigate the relationship between components of body composition and bone parameters in IBD patients. Methods: This is a cross-sectional, retrospective study including 80 IBD patients (43 women, 37 men). Lumbar spine (LS), femoral neck (FN) and whole body DXA scans were performed to analyze regional bone mineral density (BMD), as well as body composition, including appendicular skeletal muscle mass index (ASMI), total and visceral fat mass (VAT). Trabecular bone score (TBS) was assessed using iNsight Software. Results: Twenty (25%) IBD patients had inadequate LS-BMD z scores (<=−2DS). Lean mass (LM) was a significant determinant of LS-BMD, after adjusting for age, gender, BMI and fat mass (p < 0.01), while fat mass% remained associated with FN-BMD (p < 0.01). TBS correlated positively with BMI (r = 0.24, p < 0.05), LS-BMD (r = 0.56, p < 0.001), ASMI (r = 0.34, p < 0.001) and negatively with VAT/total fat% (r = −0.27, p < 0.05). Multivariate analysis showed that ASMI, LS-BMD (positively) and VAT/total fat% (negatively) were independently associated with TBS. Conclusions: In IBD patients, skeletal muscle mass and fat percentage and distribution are important factors associated with bone health.

Dissociation of Bone Resorption and Formation in Spaceflight and Simulated Microgravity: Potential Role of Myokines and Osteokines?

The dissociation of bone formation and resorption is an important physiological process during spaceflight. It also occurs during local skeletal unloading or immobilization, such as in people with neuromuscular disorders or those who are on bed rest. Under these conditions, the physiological systems of the human body are perturbed down to the cellular level. Through the absence of mechanical stimuli, the musculoskeletal system and, predominantly, the postural skeletal muscles are largely affected. Despite in-flight exercise countermeasures, muscle wasting and bone loss occur, which are associated with spaceflight duration. Nevertheless, countermeasures can be effective, especially by preventing muscle wasting to rescue both postural and dynamic as well as muscle performance. Thus far, it is largely unknown how changes in bone microarchitecture evolve over the long term in the absence of a gravity vector and whether bone loss incurred in space or following the return to the Earth fully recovers or partly persists. In this review, we highlight the different mechanisms and factors that regulate the humoral crosstalk between the muscle and the bone. Further we focus on the interplay between currently known myokines and osteokines and their mutual regulation.

Does Zoledronic Acid Improve Appendicular Lean Mass in Older Women with Osteoporosis? A Sub-Analysis of a Randomized Clinical Trial

BACKGROUND

Coexistence of osteoporosis and sarcopenia (osteosarcopenia), is associated with increased risk for fractures, falls, and mortality. Although there are multiple medications for management of osteoporosis, there are no approved pharmacotherapy for sarcopenia.

OBJECTIVES

We examined the effect of zoledronic acid on muscle mass indices including ALM (Appendicular Lean Mass) and ALM/Height2 in a cohort of older women with osteoporosis who were residents of Long-Term Care Communities (LTCCs).

DESIGN

A secondary analysis of a 2-year double-blind, randomized, placebo-controlled clinical trial.

SETTING

Residents of LTCCs.

PARTICIPANTS

Sixty-two postmenopausal women with osteoporosis.

INTERVENTION

Participants either received 5 mg infusion of zoledronic acid or placebo, once at the start of the study.

MEASUREMENTS

Participant's ALM/Height2, ALM, total hip BMD (Bone Mineral Density) and spine BMD were measured in 6, 12 and 24 months.

RESULTS

On average, participants were 86.7 years old and had a BMI of 27.4 kg/m2. There was no significant difference in change from baseline (mean ± SE) between the treatment group and the placebo group in ALM/Height2: (-0.15 vs -0.02, p = 0.541) and (-0.17 vs 0.001, p = 0.315) and (-0.29 vs -0.19, p = 0.646) or ALM: (-0.38 vs -0.09, p = 0.455) and (-0.45 vs -0.005, p = 0.216) and (-0.70 vs -0.48, p = 0.553) at 6, 12, and 24 months respectively. In addition, after adjusting for a possible confounding, the ALM/Height2 or ALM did not have significant improvements from baseline at 6 months, 12 months, and 24 months either in the treatment group or in the placebo group. However, there were significant improvements in the BMD at the total hip and the spine in the treatment group compared with the placebo group at all three time points.

CONCLUSIONS

Among older women residing in LTCCs, a single dose of zoledronic acid did not increase ALM/Height2 and ALM, despite improving the BMD at the total hip and the spine at the 2-year follow-up.

Secretome from In Vitro Mechanically Loaded Myoblasts Induces Tenocyte Migration, Transition to a Fibroblastic Phenotype and Suppression of Collagen Production

It is known that mechanical loading of muscles increases the strength of healing tendon tissue, but the mechanism involved remains elusive. We hypothesized that the secretome from myoblasts in co-culture with tenocytes affects tenocyte migration, cell phenotype, and collagen (Col) production and that the effect is dependent on different types of mechanical loading of myoblasts. To test this, we used an in vitro indirect transwell co-culture system. Myoblasts were mechanically loaded using the FlexCell^® Tension system. Tenocyte cell migration, proliferation, apoptosis, collagen production, and several tenocyte markers were measured. The secretome from myoblasts decreased the Col I/III ratio and increased the expression of tenocyte specific markers as compared with tenocytes cultured alone. The secretome from statically loaded myoblasts significantly enhanced tenocyte migration and Col I/III ratio as compared with dynamic loading and controls. In addition, the secretome from statically loaded myoblasts induced tenocytes towards a myofibroblast-like phenotype. Taken together, these results demonstrate that the secretome from statically loaded myoblasts has a profound influence on tenocytes, affecting parameters that are related to the tendon healing process.

Muscle-derived factors influencing bone metabolism

A significant amount of attention has been brought to the endocrine-like function of skeletal muscle on various tissues, particularly with bone. Several lines of investigation indicate that the physiology of both bone and muscle systems may be regulated by a given stimulus, such as exercise, aging, and inactivity. Moreover, emerging evidence indicates that bone is heavily influenced by soluble factors derived from skeletal muscle (i.e., muscle-to-bone communication). The purpose of this review is to discuss the regulation of bone remodeling (formation and/or resorption) through skeletal muscle-derived cytokines (hereafter myokines) including the anti-inflammatory cytokine METRNL and pro-inflammatory cytokines (e.g., TNF-α, IL-6, FGF-2 and others). Our goal is to highlight possible therapeutic opportunities to improve muscle and bone health in aging.

Osteosarcopenia in Very Old Age Adults After Hip Fracture: A Real-World Therapeutic Standpoint

Loss of bone and muscle mass and strength (i. e., osteosarcopenia) is a highly prevalent clinical condition in older adults, associated with an increased risk of fragility fractures and unfavorable clinical outcomes. Although sarcopenia is a potential risk factor for osteoporosis and subsequent fracture, and the management of this hazardous duet is the key to preventing osteoporotic fracture, evidence pertaining to the treatment of sarcopenia for the purpose of preventing fragile fractures remains insufficient. Given this scenario we aimed at prospectively compare the long-term effectiveness of bisphosphonates vs. denosumab, on bone and muscle, in a cohort of old age hip fractured patients by virtue of a timely osteo-metabolic and sarcopenic assessment. Ninety-eight patients consecutively enrolled at the IRCCS Hospital San martino, Genoa, Italy, received at baseline comprehensive geriatric assessment and Bone Densitometry (DXA) with the quantitative and quantitative bone analysis and evaluation of relative skeletal muscle index (RSMI) and longitudinally after 1 year form hip surgery. The results showed a slightly and non-significant osteo-metabolic improvement in the Alendronate group compared to the Denosumab group, and a positive trend of RSMI measurements in the Denosumab group. Although preliminary in nature, this is the first report to longitudinally analyze osteosarcopenia in a real-world cohort of very old age patients after hip fracture and moved a step forward in the understanding of the best osteo-metabolic therapy for long- term treatment, exploring as well the potential dual role of denousumab as antiresorptive and muscle strength specific drug for osteosarcopenia in this vulnerable population.

Impact of Intrinsic Muscle Weakness on Muscle-Bone Crosstalk in Osteogenesis Imperfecta

Bone and muscle are highly synergistic tissues that communicate extensively via mechanotransduction and biochemical signaling. Osteogenesis imperfecta (OI) is a heritable connective tissue disorder of severe bone fragility and recently recognized skeletal muscle weakness. The presence of impaired bone and muscle in OI leads to a continuous cycle of altered muscle-bone crosstalk with weak muscles further compromising bone and vice versa. Currently, there is no cure for OI and understanding the pathogenesis of the skeletal muscle weakness in relation to the bone pathogenesis of OI in light of the critical role of muscle-bone crosstalk is essential to developing and identifying novel therapeutic targets and strategies for OI. This review will highlight how impaired skeletal muscle function contributes to the pathophysiology of OI and how this phenomenon further perpetuates bone fragility.

An analysis and systematic review of sarcopenia increasing osteopenia risk

Sarcopenia is a progressive generalized skeletal muscle disorder, which may increase the risk of osteopenia. The aim of this study was to systematically review studies on the association between sarcopenia and osteopenia by pooled analysis. The PubMed and Embase databases were searched from inception to October 2020 for studies focusing on the association between sarcopenia and osteopenia. Two reviewers independently extracted data and assessed study quality. A pooled analysis was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs) using random-effects models. Subgroup analysis was conducted to explore the source of heterogeneity and the stability of outcome. A total of 25 independent studies involving 47,744 participants fulfilled the inclusion criteria. Sarcopenia significantly increased the risk of osteopenia (OR, 2.08; 95% CI, 1.66–2.60); Sensitivity analyses indicated the outcome was stable. Subgroup analyses showed that sarcopenia significantly increased osteopenia risk in each subgroup. No evidence of publication bias among the studies existed. In this study, our findings showed that sarcopenia significantly increased the risk of osteopenia. Thus, we suggest that sarcopenia can be a predictor of osteopenia risk.

Musculoskeletal Health in Premature Ovarian Insufficiency. Part One: Muscle

Accelerated bone loss and muscle decline coexist in women with premature ovarian insufficiency (POI), but there are significant gaps in our understanding of musculoskeletal health in POI. This article is the first of a two-part review which describes estrogen signaling in muscle and its role in musculoskeletal health and disease. Current evidence regarding the utility of available diagnostic tests and therapeutic options is also discussed. A literature review from January 2000 to March 2020 was conducted to identify relevant studies. Women with POI experience significant deterioration in musculoskeletal health due to the loss of protective effects of estrogen. In addition to bone loss, muscle decay and dysfunction is now increasingly recognized. Nevertheless, there is a paucity of validated tools to assess muscle parameters. There is a growing need to acknowledge bone-muscle codependence to design new therapies which target both muscle and bone, resulting in improved physical performance and reduced morbidity and mortality. More high-quality research and international collaborations are needed to address the deficiencies in our understanding and management of musculoskeletal health in women with POI.

Muscle-Bone Crosstalk in Chronic Obstructive Pulmonary Disease

Sarcopenia and osteoporosis are common musculoskeletal comorbidities of chronic obstructive pulmonary disease (COPD) that seriously affect the quality of life and prognosis of the patient. In addition to spatially mechanical interactions, muscle and bone can also serve as endocrine organs by producing myokines and osteokines to regulate muscle and bone functions, respectively. As positive and negative regulators of skeletal muscles, the myokines irisin and myostatin not only promote/inhibit the differentiation and growth of skeletal muscles, but also regulate bone metabolism. Both irisin and myostatin have been shown to be dysregulated and associated with exercise and skeletal muscle dysfunction in COPD. During exercise, skeletal muscles produce a large amount of IL-6 which acts as a myokine, exerting at least two different conflicting functions depending on physiological or pathological conditions. Remarkably, IL-6 is highly expressed in COPD, and considered to be a biomarker of systemic inflammation, which is associated with both sarcopenia and bone loss. For osteokines, receptor activator of nuclear factor kappa-B ligand (RANKL), a classical regulator of bone metabolism, was recently found to play a critical role in skeletal muscle atrophy induced by chronic cigarette smoke (CS) exposure. In this focused review, we described evidence for myokines and osteokines in the pathogenesis of skeletal muscle dysfunction/sarcopenia and osteoporosis in COPD, and proposed muscle-bone crosstalk as an important mechanism underlying the coexistence of muscle and bone diseases in COPD.

Masticatory muscle function affects the pathological conditions of dentofacial deformities

The causes of dentofacial deformities include various known syndromes, genetics, environmental and neuromuscular factors, trauma, and tumors. Above all, the functional effects of muscles are important, and deformation of the mandible is often associated with a mechanical imbalance of the masticatory muscles. With the vertical position of the face, weakness of the sling of the masseter muscle and medial pterygoid muscle causes dilatation of the mandibular angle. In patients with a deep bite, excessive function of the masticatory muscles is reported. Myosin heavy chain　(MyHC) properties also affect jawbone morphology. In short-face patients, the proportion of type II fibers, which are fast muscles, is high. The proportions of muscle fiber types are genetically determined but can be altered by postnatal environmental factors. Orthognathic surgery may results in the transition of MyHC to type II (fast) fibers, but excessive stretching enhances the release of inflammatory mediators and causes a shift toward a greater proportion of slow muscle fibers. This feature can be related to postoperative relapse. Bones and muscles are in close crosstalk, and it may be possible to use biochemical approaches as well as biomechanical considerations for the treatment of jaw deformities.

The Osteocyte: New Insights

Osteocytes are an ancient cell, appearing in fossilized skeletal remains of early fish and dinosaurs. Despite its relative high abundance, even in the context of nonskeletal cells, the osteocyte is perhaps among the least studied cells in all of vertebrate biology. Osteocytes are cells embedded in bone, able to modify their surrounding extracellular matrix via specialized molecular remodeling mechanisms that are independent of the bone forming osteoblasts and bone-resorbing osteoclasts. Osteocytes communicate with osteoclasts and osteoblasts via distinct signaling molecules that include the RankL/OPG axis and the Sost/Dkk1/Wnt axis, among others. Osteocytes also extend their influence beyond the local bone environment by functioning as an endocrine cell that controls phosphate reabsorption in the kidney, insulin secretion in the pancreas, and skeletal muscle function. These cells are also finely tuned sensors of mechanical stimulation to coordinate with effector cells to adjust bone mass, size, and shape to conform to mechanical demands.

Bone-Muscle Mutual Interactions

PURPOSE OF REVIEW

The purpose of this review is to describe the current state of our thinking regarding bone-muscle interactions beyond the mechanical perspective.

RECENT FINDINGS

Recent and prior evidence has begun to dissect many of the molecular mechanisms that bone and muscle use to communicate with each other and to modify each other's function. Several signaling factors produced by muscle and bone have emerged as potential mediators of these biochemical/molecular interactions. These include muscle factors such as myostatin, Irisin, BAIBA, IL-6, and the IGF family and the bone factors FGF-23, Wnt1 and Wnt3a, PGE2, FGF9, RANKL, osteocalcin, and sclerostin. The identification of these signaling molecules and their underlying mechanisms offers the very real and exciting possibility that new pharmaceutical approaches can be developed that will permit the simultaneous treatments of diseases that often occur in combination, such as osteoporosis and sarcopenia.